COVID-19 vaccine: Canadian Immunization Guide

For health professionals

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This chapter has not yet been updated with the following following summary and statement from the National Advisory Committee on Immunization (NACI):

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Key information (refer to text and tables for details)

What

Who

How

Why

Epidemiology

Disease description

Infectious agent

COVID-19 is caused by the SARS-CoV-2, which was first recognized in Wuhan, China in December 2019.

Transmission

Current evidence suggests that SARS-CoV-2 is spread through respiratory droplets and aerosols created when an infected person breathes, coughs, sneezes, sings, shouts, or talks. A person may be infectious for up to 3 days before showing symptoms.

More information on the transmission of SARS-CoV-2 can be found on the Public Health Agency of Canada (PHAC) webpages for COVID-19: Main modes of transmission.

Variants of concern

Genetic mutations in the SARS-CoV-2 virus have been identified, some of which make the virus more infectious and transmissible. They may also affect the severity of disease and the level of protection offered by vaccines.

More information on the variants of concern (VOC) reported in Canada is available in the COVID-19 epidemiology update. The COVID-19 Weekly Epidemiological Update by the World Health Organization (WHO) provides a summary on the global distribution and emerging evidence on VOC and variants of interest (VOI). Differences between VOC and VOI are available from SARS-CoV-2 variants: National definitions, classifications and public health actions.

Risk factors

Anyone can be infected with SARS-CoV-2. However, some populations are at increased risk of exposure to the virus (e.g., due to living or occupational settings), and some populations are at increased risk of severe disease and outcomes (e.g., hospitalization and death) due to biological factors (e.g., advanced age, pre-existing medical conditions, pregnancy) and social factors (e.g., socioeconomic status, belonging to a racialized population) that may intersect. Exposure and risk of severe disease factors may overlap, further increasing risk. Any combination of these factors, as well as varying access to health care services, has the potential for disproportionate consequences for specific populations characterized by increased rates of infection and disease, severe illness, hospitalizations, and/or deaths.

There is a spectrum of COVID-19 disease severity, ranging from asymptomatic to mild, moderate, severe and critical disease. Severe disease more often occurs in those with increasing age and those with underlying medical conditions, with the risk increasing with the number of underlying conditions. A list of underlying medical conditions associated with more severe COVID-19 disease can be found in COVID-19 signs, symptoms and severity of disease: A clinician guide.

There is limited evidence on clinical risk factors for severe COVID-19 disease in pediatric populations. Children at increased risk for severe outcomes may include children who are obese, children who are medically fragile/ have medical complexities, children with more than one comorbidity, children with neurological disorders, and children with immune dysregulation associated with Down syndrome (Trisomy 21) and other immunocompromising conditions.

Adolescents 12 to 17 years of age who may be at high risk of severe illness due to COVID-19 include those with one or more of the following underlying medical conditions (based on expert opinion and evolving evidence):

Spectrum of clinical illness

The median incubation period (the time from exposure to symptom onset) for non-variant SARS-CoV-2 has been estimated to be 5 to 6 days, with most individuals (97.5%) developing symptoms within 11.5 days of exposure. The incubation period ranges from 1 to 14 days.

Clinical presentation and symptoms of COVID-19 vary in frequency and severity. To date, there is no list of symptoms that has been validated to have high specificity or sensitivity for COVID-19.

More information on the spectrum of clinical illness is available on the PHAC webpage for COVID-19 signs, symptoms and severity of disease: A clinician guide.

While most children and adolescents with COVID-19 have mild or no symptoms, some do experience severe disease. However, children and adolescents report few severe outcomes of COVID-19 (i.e., hospitalizations due to COVID-19, ICU admission, and deaths) compared to older age groups.

Children, adolescents and adults with SARS-CoV-2 infection are also at risk of multisystem inflammatory syndrome (MIS), a rare but serious condition that can occur several weeks following SARS-CoV-2 infection.

Disease incidence

Global

Updated international data on COVID-19 cases and deaths is available.

Weekly epidemiological updates highlighting key global, regional and country-level data on COVID-19 cases and deaths are available from WHO.

National

Updated national, provincial and territorial-level data on COVID-19 cases and deaths in Canada over time is available from the PHAC webpage on Coronavirus disease (COVID-19): Outbreak update.

Preparations authorized for use in Canada

When referring to COVID-19 vaccines throughout this chapter, only those currently authorized by Health Canada for use in Canada are included. Refer to Vaccination of specific populations, Persons new to Canada for information regarding non-Health Canada authorized vaccines.

mRNA vaccines

There are currently no data on the use of bivalent Omicron-containing mRNA COVID-19 vaccines as part of a primary series and none are authorized for a primary series. NACI continues to recommend a primary series with an original mRNA vaccine in all authorized age groups.

COVID-19 vaccines that use mRNA platforms contain modified nucleotides that code for the SARS-CoV-2 spike protein. A lipid nanoparticle formulation delivers the mRNA into the recipient's cells. Once inside the cytoplasm of a cell, the mRNA provides instructions to the cell's protein production machinery to produce the trans-membrane spike protein antigen that becomes anchored on the cell's external surface. The mRNA does not enter the nucleus of the cell and does not interact with, or alter, human DNA. The immune system is engaged by both the transmembrane spike protein and immune receptors carrying spike antigens to induce humoral and cellular immune responses. The mRNA, lipid nanoparticle, and spike protein are degraded or excreted within days to weeks from time of immunization. mRNA vaccines are not live vaccines and cannot cause infection in the host.

Protein subunit vaccine

Novavax Nuvaxovid consists of a purified full-length SARS-CoV-2 recombinant spike protein nanoparticle administered as a co-formulation with the adjuvant Matrix-M. Matrix-M is a novel saponin-based adjuvant that facilitates activation of the cells of the innate immune system, which enhances the magnitude of the spike protein-specific immune response. Matrix-M has been used in Novavax Nuvaxovid clinical trials and in pre-licensure studies targeting other pathogens, but has not previously been used in any licensed vaccine.

Virus-like particle (VLP) vaccine

The Medicago Covifenz COVID-19 vaccine is an adjuvanted vaccine consisting of recombinant SARS-CoV-2 spike glycoproteins stabilized in the prefusion conformation that are produced by transient expression in Nicotiana benthamiana plants and become membrane imbedded in self-assembled enveloped VLP. The vaccine also contains Adjuvant System 03 (AS03), produced by GlaxoSmithKline, that was used as the adjuvant in three influenza vaccines: Prepandrix (H5N1), Pandemrix (H1N1pdm09) and Arepanrix (H1N1pdm09).

Viral vector (non-replicating) vaccines

COVID-19 vaccines based on viral vector platforms use a modified virus to carry genes that encode SARS-CoV-2 spike proteins into the host cells. The vector virus is a type of adenovirus that has been modified to carry COVID-19 genes and to prevent replication of the adenovirus so that it does not cause disease. Once inside the cell, the SARS-CoV-2 spike protein genes are transcribed into mRNA in the nucleus and translated into proteins in the cytosol of the cell. The AstraZeneca Vaxzevria vaccine uses a modified chimpanzee adenovirus vector (ChAd) and the Janssen Jcovden vaccine uses a modified human adenovirus serotype 26 vector (Ad26).

Health Canada authorized 2 manufacturers to produce the viral vector vaccine developed by AstraZeneca and Oxford University: AstraZeneca and Serum Institute of India (SII). Health Canada deemed the SII COVISHIELD and AstraZeneca Vaxzevria vaccines to be comparable. The authorization by interim order has expired for COVISHIELD and therefore it is no longer authorized for use or available in Canada.

Anti-SARS-CoV-2 monoclonal antibodies authorized for pre-exposure prophylaxis of COVID-19

Tixagevimab and cilgavimab are two recombinant human monoclonal antibodies with amino acid substitutions to extend antibody half-life and thus duration of protection, as well as minimize the potential risk of antibody-dependent enhancement of disease.

For complete prescribing information for any of the Preparations authorized for use in Canada, consult the product leaflet or information contained within Health Canada's authorized product monographs available through the Drug Product Database.

Immunogenicity, efficacy and effectiveness

Immunogenicity

No immunological correlate of protection has been determined for SARS-CoV-2; therefore, all immunological evidence in support of vaccine efficacy is indirect.

All COVID-19 vaccines induce humoral immune responses, including binding and neutralizing antibody responses. Some vaccines induce higher immune responses in younger populations. Viral vector-based vaccines may induce anti-vector immune responses, which may impact future vaccine efficacy (with subsequent viral vector vaccines) and effectiveness and may vary by age, dose, and interval between doses.

All authorized COVID-19 vaccines have been shown to produce cellular immune responses in adult populations.

Efficacy and effectiveness

Efficacy against symptomatic COVID-19 disease

Efficacy and effectiveness against symptomatic infection varies by variants. Protection against more severe COVID-19 outcomes is higher and better maintained over time. Clinical trials for original COVID-19 vaccines were conducted prior to the emergence of Omicron, and have substantially lower vaccine effectiveness against symptomatic infection for Omicron and related variants due to partial immune escape. Vaccine effectiveness of bivalent Omicron-containing mRNA COVID-19 vaccines has yet to be established.

In clinical trials, the original mRNA COVID-19 vaccines have been shown to be highly efficacious (approximately 74 to 95%) in the short term against confirmed symptomatic COVID-19 disease. There is similar efficacy in adults with 1 or more comorbidities, as well as in children (5 to 11 years), adolescents (12 to 15 years), younger adults and older adults. There is some evidence of waning of immunogenicity and effectiveness over time that varies by age and vaccine interval. The original mRNA vaccines are efficacious in individuals aged 12 years and over with or without evidence of prior SARS-CoV-2 infection. Efficacy estimates for the Pfizer-BioNTech Comirnaty original (10 mcg) vaccine and for the Moderna Spikevax original (50 mcg) vaccine in children aged 5 to 11 and 6 to 11 years, respectively, with evidence of prior SARS-CoV-2 infection are not currently known.

Vaccine efficacy was assessed among children aged 6 months to 5 years following one and two doses of Moderna Spikevax (25 mcg) mRNA COVID-19 vaccine during a time when Omicron was the predominant variant of SARS-CoV-2. Efficacy against confirmed symptomatic infection starting 14 days after dose 2 was also determined among participants regardless of evidence of prior SARS-CoV-2 infection and was estimated at 50.6% among study participants aged 6 to 23 months and 36.5% among participants aged 2 to 5 years. The estimate of vaccine efficacy against asymptomatic infection after 2 doses should be interpreted with caution as this finding could reflect infection acquired at any time after dose 1 prior to the time of sample collection, and may be an underestimation of 2-dose efficacy.

Clinical trial data available to date have shown that Novavax Nuvaxovid COVID-19 vaccine is highly efficacious (approximately 90%) in preventing confirmed symptomatic COVID-19 disease in the short term. Novavax Nuvaxovid has also been shown to be highly efficacious (approximately 86% to 93%) in the short term against confirmed symptomatic COVID-19 disease due to the Alpha VOC and 48.6% efficacious against the Beta variant.

Clinical trial data available to date have shown that Medicago Covifenz is efficacious (approximately 71%) in preventing confirmed symptomatic COVID-19 disease in the short-term starting at one to two weeks after receiving the full two-dose series, in populations where the Delta and Gamma VOC were predominantly in circulation. No efficacy or effectiveness data are available for Medicago Covifenz against the ancestral SARS-CoV-2 strain or the Omicron variant.

The AstraZeneca Vaxzevria COVID-19 vaccine has shown moderate short-term efficacy (approximately 62%) against symptomatic COVID-19 disease in adults 18 to 64 years of age, with increased efficacy as the interval between doses increases. The Janssen Jcovden COVID-19 vaccine demonstrated moderate efficacy against symptomatic confirmed moderate to severe COVID-19 infection from 14 days and 28 days post-vaccination of approximately 66% and 67% respectively in the primary analysis, prior to the emergence of SARS-CoV-2 variants. Estimates in the final analysis inclusive of variants, against moderate to severe COVID-19 at least 14 and 28 days after vaccination, were approximately 56% and 53%, respectively. There are no data on the efficacy of viral vector vaccines in individuals with evidence of prior SARS-CoV-2 infection.

Studies about the duration of protection provided by COVID-19 vaccination are ongoing. Decreased protection against infection over time has been noted to occur with mRNA vaccines, the protein subunit vaccine and the viral vector vaccines. Studies of vaccine efficacy against symptomatic infection after vaccination with the primary series suggest that protection with Moderna Spikevax original may be more durable than with Pfizer-BioNTech Comirnaty original vaccine. Shorter intervals between the first and second dose of a 2-dose COVID-19 vaccine series result in lower initial titres that may result in protection that decreases sooner. Observational studies show a reduction in vaccine effectiveness against SARS-CoV-2 infection and COVID-19 in immunocompromised adults when compared to the general population with a 2-dose vaccine series.

Efficacy and effectiveness against severe disease

The clinical trials of the authorized and available COVID-19 vaccines assessed efficacy against severe COVID-19 disease, but not all provided sufficient data to be able to assess the efficacy against hospitalizations or deaths.

Real world evidence suggests moderate to high vaccine effectiveness at preventing severe illness, such as hospitalization and death, which is sustained out to at least 6 months in most populations ages 12 years and more, including in older and frail populations. There is some decline noted in older adults (such as those 80 years of age and over) and residents in long term care homes in overall effectiveness over time, although protection against severe outcomes appears to be more durable than protection against infection. Effectiveness estimates suggest the Pfizer-BioNTech Comirnaty (10 mcg) original vaccine in children 5 to 11 years of age for the primary series is similarly effective against Omicron as it is in older populations. Vaccine effectiveness is unknown for Moderna Spikevax original (50 mcg) vaccine in children 6 to 11 years of age, Novavax Nuvaxovid and Medicago Covifenz. There were no deaths or cases of severe COVID-19 among trial participants 6 months to 5 years of age for the Moderna Spikevax original (25 mcg) vaccine. Therefore, efficacy against outcomes of severe COVID-19 could not be estimated.

An ad-hoc analysis examined vaccine efficacy by moderate and by moderate or severe COVID-19 for Medicago Covifenz. Estimates of efficacy against moderate or severe COVID-19 at least 7 days after dose 2 was 78.1% in the per-protocol analysis.

No clinical data are currently available for Pfizer-BioNTech Comirnaty BA.4/5 Bivalent (30 mcg), and thus the regulatory review process was centered around preclinical immunogenicity data from the Pfizer-BioNTech Comirnaty BA.4/5 Bivalent vaccine, as well as indirect clinical data from the use of the Pfizer-BioNTech Comirnaty BA.1 Bivalent (30 mcg) and Pfizer-BioNTech Comirnaty BA.1 Monovalent (30 mcg) vaccines in clinical trials.

Effectiveness against hospitalization due to MIS-C

Real world evidence suggests the Pfizer-BioNTech Comirnaty COVID-19 original vaccine has high vaccine effectiveness at preventing hospitalization due to MIS-C among adolescents 12 to 18 years of age. Effectiveness estimates against hospitalization due to MIS-C for the Pfizer-BioNTech Comirnaty (10 mcg) original vaccine in children aged 5 to 11, or for the Moderna Spikevax original (50 mcg) vaccine in children aged 6 to 11 years are not currently known. There were no cases of MIS-C among trial participants 6 months to 5 years of age for the Moderna Spikevax original (25 mcg) vaccine; however, one case of MIS-C was reported in a placebo recipient after the data cut-off. Therefore, efficacy against MIS-C was not evaluated.

There are no results specific to other COVID-19 vaccines yet, however studies are ongoing.

Efficacy and effectiveness against asymptomatic infection

Clinical trials for currently authorized COVID-19 vaccines were primarily designed to evaluate efficacy against symptomatic illness and conducted prior to the emergence of Omicron. Data on efficacy and effectiveness against asymptomatic infection remain limited.

Estimates of vaccine effectiveness for the Pfizer-BioNTech Comirnaty COVID-19 original vaccine against asymptomatic infection were moderate to high after the first dose and high after the second dose, however this was limited to adults. There are no current effectiveness estimates against asymptomatic COVID-19 for the Pfizer-BioNTech Comirnaty original vaccine in adolescent or pediatric populations under the age of 18 years.

Preliminary data from the ongoing Moderna Spikevax COVID-19 vaccine (original) trial in adults 18 years of age and older showed a lower prevalence of SARS-CoV-2 positivity by polymerase chain reaction (PCR) in asymptomatic participants at one particular time point (after dose 1 but before dose 2), and therefore viral shedding, in the group that received the vaccine compared to the placebo group. However, the current data are insufficient to draw definitive conclusions. Among adolescents aged 12 to 17 years, Moderna Spikevax original had low protection against asymptomatic infection starting 14 days after dose 2, noting the confidence interval around the point estimate was wide and included zero. Among children aged 6 to 11 years, Moderna Spikevax original had moderate protection against asymptomatic infection starting 14 days after dose 1.

The AstraZeneca Vaxzevria viral vector vaccine did not demonstrate efficacy against asymptomatic infection, although the number of asymptomatic infections was small. The Janssen Jcovden COVID-19 vaccine had moderate protection against asymptomatic and undetected COVID-19 infection. There are currently no efficacy estimates against asymptomatic COVID-19 infections for Novavax Nuvaxovid or Medicago Covifenz.

Recommendations for use

Children

Recommendations for children 6 months to 5 years of age

It is recommended that a complete series with Moderna Spikevax original (25 mcg) COVID-19 vaccine may be offered to children 6 months to 5 years of age who do not have contraindications to the vaccine, with a dosing interval of at least 8 weeks between the first and second dose.

It is recommended that children 6 months to 5 years of age who are moderately to severely immunocompromised may be immunized with a primary series of three doses of Moderna Spikevax original (25 mcg) COVID-19 vaccine, using an interval of 4 to 8 weeks between each dose.

Recommendations for children 5 to 11 years of age

It is recommended that a complete series with an mRNA COVID-19 vaccine should be offered to children in the authorized age groups without contraindications to the vaccine, with a dosing interval of at least 8 weeks between the first and second dose.

For children 5 to 11 years of age, the use of Pfizer-BioNTech Comirnaty original (10 mcg) COVID-19 vaccine is preferred to Moderna Spikevax original (25 mcg or 50 mcg, as per authorized age) to start or continue the primary vaccine series. However, Moderna Spikevax original (25 mcg or 50 mcg, as per authorized age) vaccine may be offered as an alternative.

Children who have received Moderna Spikevax original (25 mcg) for a previous dose and turn 6 prior to completing their primary series are recommended to receive Moderna Spikevax original (50 mcg) to complete their primary series. If the primary series was completed with Moderna Spikevax original (25 mcg) or with Pfizer-BioNTech Comirnaty original (10 mcg), the dose should be considered valid and the series complete.

Recommendations for children 5 to 11 years of age who are moderately to severely immunocompromised

It is recommended that children 5 to 11 years of age who are moderately to severely immunocompromised should be immunized with a primary series of 3 doses of an mRNA COVID-19 vaccine authorized for their age, using an interval of 4 to 8 weeks between each dose.

Indirect data from adult populations (≥18 years of age) on original mRNA COVID-19 vaccines suggest Moderna Spikevax original (100 mcg) may result in higher vaccine effectiveness after a 2-dose primary series compared to Pfizer-BioNTech Comirnaty original (30 mcg) and is associated with a higher seroconversion rate among adult immunocompromised patients. Given this potential benefit, administration of the Moderna Spikevax original (50 mcg or 25 mcg) vaccine as a 3-dose primary series may be considered for some children 5 to 11 years of age who are moderately to severely immunocompromised, as per the authorized age group.

For children 6 months to 11 years of age who are moderately to severely immunocompromised who have previously received a 2-dose series with an mRNA COVID-19 vaccine, it is recommended that a third dose should be offered 4 to 8 weeks after the second dose.

Considerations

The Pfizer-BioNTech Comirnaty original vaccine is authorized for children 5 to 11 years of age as a primary series of two doses of 10 mcg given 21 days apart. The Moderna Spikevax original vaccine is authorized for children 6 months to 11 years of age as a primary series of two doses (25 mcg or 50 mcg based on age for authorization) given 28 days apart. Currently, bivalent Omicron-containing mRNA COVID-19 vaccines are only authorized in adolescents and/or adult populations.

In adults, evidence suggests that longer intervals between the first and second doses of a primary series result in a stronger immune response and higher vaccine effectiveness that is expected to last longer, compared to shorter intervals. Data from older age groups also suggests an extended interval may be associated with a reduced risk of myocarditis/pericarditis following a second dose of an mRNA COVID-19 vaccine.

A longer dosing interval for most children is also currently recommended. It is important that children are given the opportunity to establish optimal long-term immunity against COVID-19.

Children who receive the 10 mcg Pfizer-BioNTech Comirnaty (original) or 50 mcg Moderna Spikevax COVID-19 vaccine (original) for their first dose and who have turned 12 years of age by the time the second dose is due may receive the 30 mcg Pfizer-BioNTech Comirnaty (original) COVID-19 vaccine or the 100 mcg Moderna Spikevax COVID-19 vaccine (original) that is authorized for individuals aged 12 years and older to complete their primary series. If the second dose of 10 mcg (Pfizer-BioNTech Comirnaty original) or 50 mcg (Moderna Spikevax original) is given, the dose should still be considered valid and the series complete. The risk of myocarditis or pericarditis with the Moderna Spikevax original (50 mcg) in children 6 to 11 years of age is unknown, given the limited use in this age group. However, in adolescents and young adults 12 years of age and older, the rare risk of myocarditis or pericarditis was higher with Moderna Spikevax original (100 mcg) than with Pfizer-BioNTech Comirnaty original (30 mcg) with a primary series.  Safety surveillance data suggests the risk of myocarditis and/or pericarditis in younger children is lower than that of adolescents or young adults. Among children 5 to 11 years of age following vaccination with Pfizer-BioNTech Comirnaty original (10 mcg), very rare cases were most often reported following the second dose and among males.

Refer to Booster doses for information on booster doses for children 5 to 11 years of age.

Adolescents

Recommendations for adolescents 12 to 17 years of age

It is recommended that a complete series with an mRNA COVID-19 vaccine should be offered to adolescents 12 to 17 years of age who do not have contraindications to the vaccine.

Refer to Booster doses for information on booster doses for adolescents 12 to 17 years of age.

Recommendations for adolescents 12 to 17 years of age who are moderately to severely immunocompromised

For moderately to severely immunocompromised adolescents 12 to 17 years of age, it is recommended a primary series of 3 doses of an mRNA vaccine should be offered.

Refer to Booster doses for information on booster doses for adolescents 12 to 17 years of age who are moderately to severely immunocompromised.

Considerations

The known risks of COVID-19 illness (including complications like myocarditis/pericarditis) outweigh the potential harms of having an adverse reaction following mRNA vaccination. The risk of myocarditis or pericarditis following mRNA vaccination is rare, relatively mild, and resolves quickly in most individuals. The use of the Pfizer-BioNTech Comirnaty original vaccine is preferred to the Moderna Spikevax original vaccine in individuals 12 to 17 years of age because of a lower reported rate of myocarditis/pericarditis following the Pfizer-BioNTech Comirnaty original (30 mcg) compared to the Moderna Spikevax original (100 mcg) vaccine. Additionally, a longer interval between doses is associated with higher vaccine effectiveness and potentially lower risk of myocarditis/pericarditis.

Adults

Recommendations for adults 18 years of age and older

It is recommended that a complete primary series with an mRNA COVID-19 vaccine should be preferentially offered to individuals in the authorized age group without contraindications to the vaccine.

There is a preferential recommendation for the use of mRNA COVID-19 vaccines in all authorized age groups due to better effectiveness of mRNA vaccines and the rare risk of certain serious adverse events with viral vector vaccines, such as vaccine-induced immune thrombotic thrombocytopenia (VITT).

The known risks of COVID-19 illness (including complications like myocarditis/pericarditis) outweigh the potential harms of having an adverse reaction following mRNA vaccination, including the rare risk of myocarditis or pericarditis which despite hospitalization, is relatively mild and resolves quickly in most individuals.

For individuals aged 18 to 29 years receiving an mRNA COVID-19 vaccine primary series:

For adults aged 30 years or older receiving an mRNA COVID-19 vaccine primary series:

It is recommended that a primary series of an authorized protein subunit COVID-19 vaccine (Novavax Nuvaxovid) or VLP COVID-19 vaccine (Medicago Covifenz) may be offered to individuals in the authorized age group without contraindications to the vaccine who are not able or willing to receive an mRNA COVID-19 vaccine.

The protein subunit COVID-19 vaccine (Novavax Nuvaxovid) is not currently authorized by Health Canada as a booster but clinical trials have been conducted. Novavax Nuvaxovid may be offered to as a booster to select populations. Informed consent when administering a Medicago Covifenz primary series should include mention that this vaccine is not currently authorized for use as a booster dose in Canada.

A viral vector COVID-19 vaccine may be offered to individuals in the authorized age group without contraindications to the vaccine only when all other authorized COVID-19 vaccines are contraindicated.

Refer to Booster doses for information regarding booster doses for adults 18 years of age and older.

Recommendations for adults 18 years of age and older who are moderately to severely immunocompromised

For moderately to severely immunocompromised adults who have not yet been immunized, it is recommended a primary series of 3 doses of an mRNA vaccine should be preferentially offered. For these individuals who have previously received a 1- or 2-dose COVID-19 vaccine series (with a homologous or heterologous schedule using mRNA or viral vector vaccines), it is recommended that an additional dose of an mRNA COVID-19 vaccine should be offered.

There is heterogeneity among those who are moderately to severely immunocompromised, and risks from COVID-19, as well as the likelihood of a reduced response to vaccines, will vary depending on age and the immunocompromising condition. Some immunocompromised individuals have a diminished immune response to the vaccines. Moderna Spikevax original (100 mcg) induces somewhat higher antibody levels compared to Pfizer-BioNTech Comirnaty original (30 mcg) and protection (against infection and severe disease) from a primary series with Moderna Spikevax original (100 mcg) may be more durable than Pfizer-BioNTech Comirnaty original (30 mcg).

Refer to Booster doses for information on booster doses for moderately to severely immunocompromised adults 18 years of age and older.

Schedule

For individuals 12 years of age and older, when the first dose in a COVID-19 vaccine series is an mRNA vaccine, the same mRNA vaccine product should be offered for the subsequent dose if readily available. When the same mRNA vaccine product is not readily available, or is unknown, another mRNA COVID-19 vaccine product recommended in that age group can be considered interchangeable and should be offered to complete the series.

For mixed COVID-19 vaccine schedules, the minimum interval between doses should be based on the minimum interval of the product used for the first dose (e.g., Pfizer-BioNTech Comirnaty original COVID-19 vaccine should be offered a minimum of 28 days after AstraZeneca Vaxzevria COVID-19 vaccine).

Recommendations on optimal intervals apply to all vaccine schedules. Longer intervals between doses are likely to result in a better immune response, higher vaccine effectiveness and potentially lower risk of myocarditis/pericarditis. An 8-week interval between the first and second dose of mRNA vaccine should be provided (Table 1).

For some individuals (including moderately to severely immunocompromised individuals) providers should aim to provide each dose of the 3 dose series 4 to 8 weeks apart from each other. An interval longer than 4 weeks between each dose is likely to result in a better immune response and duration of protection and may be associated with lower risk of myocarditis/pericarditis. However, if a longer interval between doses is being considered, then the need for earlier protection due to risk of exposure (including local transmission of SARS-CoV-2, circulation of VOC) and risk of severe disease (e.g., underlying high risk medical condition) should be taken into account. Some moderately to severely immunocompromised individuals may still be susceptible after the initial 1 or 2 doses, so their period of susceptibility until receipt of the additional dose will also increase if the interval between doses is increased. Some of these individuals will also remain susceptible after a third dose of COVID-19 vaccine.

It should be noted that the suggestion for an 8-week interval between the first and second dose of the primary series applies to those who have not yet completed a primary series and does not have implications for those who were already vaccinated with shorter or longer intervals.

Refer to Table 5 for suggested intervals between previous SARS-CoV-2 infection and COVID-19 vaccination.

Table 1. Immunization schedule for a primary series, by COVID-19 vaccine
Vaccine product Immunization scheduleTable 1 Footnote a Age indication Minimum interval Authorized interval Optimal intervalTable 1 Footnote b
Pfizer-BioNTech Comirnaty original (30 mcg) 2-dose schedule 12 years of age and older 19 daysTable 1 Footnote c 21 days 8 weeks
Pfizer-BioNTech Comirnaty original (10 mcg, pediatric formulation) 2-dose schedule 5 to 11 years of age 19 days 21 days At least 8 weeks
Moderna Spikevax original (100 mcg) 2-dose schedule 12 years of age and older 21 daysTable 1 Footnote d 28 days 8 weeks
Moderna Spikevax original (50 mcg) 2-dose schedule 6 to 11 years of age 21 daysTable 1 Footnote d 28 days At least 8 weeks
Moderna Spikevax original (25 mcg) 2-dose schedule 6 months to 5 years of age 28 daysTable 1 Footnote e 28 days At least 8 weeks
Novavax Nuvaxovid 2-dose schedule 18 years of age and older 21 daysTable 1 Footnote f 21 daysTable 1 Footnote g 8 weeks
Medicago Covifenz 2-dose schedule 18 to 64 years of age 21 daysTable 1 Footnote h 21 days 8 weeks
AstraZeneca Vaxzevria 2-dose schedule 18 years of age and older 28 days 4 to 12 weeks At least 8 weeks
Janssen Jcovden 1-dose schedule 18 years of age and older N/A N/A N/A
Table 1 Footnote a

It is recommended that for moderately to severely immunocompromised individuals, a primary series of 3 doses with an mRNA COVID-19 vaccine should be preferentially offered. Refer to Table 2 for additional information.

Return Table 1 to footnote a referrer

Table 1 Footnote b

There is evidence that longer intervals between the first and second doses of COVID-19 vaccines result in more robust and durable immune response and higher vaccine effectiveness. Balancing this enhanced protection from a longer interval with simultaneously minimizing the time at risk of infection due to having protection from only 1 dose, for all COVID-19 vaccines an 8-week (or at least 8 week) interval is recommended.

Return Table 1 to footnote b referrer

Table 1 Footnote c

The basis for this minimum interval is that the per-protocol design for the Pfizer-BioNTech Comirnaty COVID-19 vaccine clinical trial was 19 to 23 days.

Return Table 1 to footnote c referrer

Table 1 Footnote d

The basis for this minimum interval is that the majority of participants in the Moderna Spikevax COVID-19 vaccine clinical trials received the second dose 21 to 42 days after the first, as per the pre-defined window.

Return Table 1 to footnote d referrer

Table 1 Footnote e

The participants in the clinical trial received the second dose a minimum of 28 days after the first dose.

Return Table 1 to footnote e referrer

Table 1 Footnote f

The basis for this minimum interval is that the majority of participants in the Novavax Nuvaxovid clinical trial received the second dose 21+7 days after the first, as per the pre-defined window.

Return Table 1 to footnote f referrer

Table 1 Footnote g

The authorized interval was defined as 3 weeks in the product monograph.

Return Table 1 to footnote g referrer

Table 1 Footnote h

The minimum interval follows from the clinical trial protocol.

Return Table 1 to footnote h referrer

Moderately to severely immunocompromised individuals

Table 2. Immunization schedule for a primary series for moderately to severely immunocompromised individuals, by COVID-19 vaccine
Vaccine product Immunization scheduleTable 2 Footnote a Minimum interval between the initial 2-dosesTable 2 Footnote b Minimum interval between 1- or 2-dose primary series and the additional doseTable 2 Footnote b
Pfizer-BioNTech Comirnaty original (30 mcg) (10 mcg, pediatric formulation)Table 2 Footnote c 3-dose schedule 19 daysTable 2 Footnote d 28 days
Moderna Spikevax original (100 mcg) (50 mcg)Table 2 Footnote e 3-dose schedule 21 daysTable 2 Footnote f 28 days
Moderna Spikevax original (25 mcg) 3-dose schedule 28 daysTable 2 Footnote h 28 days
Novavax NuvaxovidTable 2 Footnote h 2-3 dose schedule 21 days 28 days
Medicago CovifenzTable 2 Footnote g 2-3 dose schedule 21 days 28 days
AstraZeneca Vaxzevria 2-dose scheduleTable 2 Footnote i +1 mRNA 28 days 28 days
Janssen Jcovden 1-dose scheduleTable 2 Footnote i +1 mRNA N/A 28 days
Table 2 Footnote a

It is recommended that for moderately to severely immunocompromised individuals, a primary series of 3 doses with an mRNA COVID-19 vaccine should be preferentially offered. For these individuals who have previously received a 1- or 2-dose COVID-19 vaccine series (with a homologous or heterologous schedule using mRNA or viral vector vaccines), it is recommended that an additional dose of an mRNA COVID-19 vaccine should be offered.

Table 2 Return to footnote a referrer

Table 2 Footnote b

For immunocompromised individuals, providers should aim to provide each dose of the 2 or 3 dose primary series 4 to 8 weeks apart from each other. An interval longer than 4 weeks between each dose is likely to result in a better immune response and duration of protection, and may be associated with a lower risk of myocarditis/pericarditis. However, if a longer interval is being considered, risk factors for exposure and risk of severe disease should also be taken into account.

Table 2 Return to footnote b referrer

Table 2 Footnote c

The 30 mcg dose of Pfizer-BioNTech Comirnaty original COVID-19 vaccine is authorized for those 12 years of age and older. The 10 mcg dose of Pfizer-BioNTech Comirnaty original COVID-19 vaccine is authorized for those 5 to 11 years of age.

Table 2 Return to footnote c referrer

Table 2 Footnote d

The basis for this minimum interval is that the per-protocol design for the Pfizer-BioNTech Comirnaty original COVID-19 vaccine clinical trial was 19 to 23 days.

Table 2 Return to footnote d referrer

Table 2 Footnote e

The 100 mcg dose of Moderna Spikevax original COVID-19 vaccine is authorized for those 12 years of age and older. The 50 mcg dose of Moderna Spikevax original COVID-19 vaccine is authorized for those 6 to 11 years of age.

Table 2 Return to footnote e referrer

Table 2 Footnote f

The basis for this minimum interval is that the majority of participants in the Moderna Spikevax original COVID-19 vaccine clinical trials received the second dose 21 to 42 days after the first, as per the pre-defined window.

Table 2 Return to footnote f referrer

Table 2 Footnote g

The participants in the clinical trial received the second dose a minimum of 28 days after the first dose.

Table 2 Return to footnote g referrer

Table 2 Footnote h

mRNA COVID-19 vaccines are preferred and are authorized for a 3-dose primary series in moderately to severely immunocompromised individuals, while Novavax Nuvaxovid and Medicago Covifenz are not currently authorized as a 3-dose primary series in these populations. Based on clinical discretion, a protein subunit or virus-like particle vaccine may be offered as a 3-dose primary series for moderately to severely immunocompromised individuals in the authorized age group who are not able or willing to receive an mRNA COVID-19 vaccine.

Table 2 Return to footnote h referrer

Table 2 Footnote i

An initial or additional dose of a viral vector vaccine should only be considered for those in the authorized age group, when all other authorized COVID-19 vaccines are contraindicated.

Table 2 Return to footnote i referrer

Booster doses

Evidence suggests that protection against infection decreases with time from receipt of the last dose of vaccine, especially if there are shorter intervals between doses which may result in lower immune responses and more rapid waning of protection. Booster doses provides additional protection, including and especially against severe disease. However, the duration of protection is currently unknown, and the absolute benefit will depend on the residual protection from the booster dose and on the level of circulating disease in the community.

Booster doses of an authorized COVID-19 vaccine are recommended at specified intervals after a previous COVID-19 vaccine dose or SARS-CoV-2 infection, regardless of the product offered (see Table 5). An mRNA COVID-19 vaccine dose is preferred for the booster dose. Recipients of a viral vector vaccine series completed with only viral vector vaccines (AstraZeneca or Janssen Jcovden COVID-19 vaccine) should receive booster doses with an mRNA vaccine.

All doses of COVID-19 vaccines after the primary series, are described as booster doses. Note that for moderately to severely immunocompromised individuals, the primary series included one additional dose that is not referred to as a booster dose. Among those who are moderately to severely immunocompromised, there is heterogeneity. Risks from COVID-19, as well as the likelihood of a reduced response to vaccines, will vary depending on age and the immunocompromising condition and some immunocompromised individuals have a diminished immune response to COVID-19 vaccines. While data on booster doses of a COVID-19 vaccine after the recommended three-dose primary series in moderately to severely immunocompromised individuals are currently limited, many of these individuals are at a higher risk of severe outcomes of COVID-19 and also at increased risk of decreasing protection over time since vaccination.

Bivalent vaccines are the preferred vaccine for booster doses among individuals in the authorized age groups, as they contain Omicron, which is the most antigenically-distinct variant from the original SARS-CoV-2 strain.

Refer to Administration practices, Pre-vaccination counselling and Safety and adverse events for further information.

Timing of booster doses

COVID-19 booster doses may be offered at an interval of 6 months after a previous COVID-19 vaccine dose or SARS-CoV-2 infection, regardless of the product offered. However, a shorter interval of at least 3 months may be warranted in the context of heightened epidemiologic risk, as well as operational considerations for the efficient deployment of the vaccine program.

Table 3. Options and considerations for vaccine types and doses offered for COVID-19 booster doses for certain populations
Population Vaccine type (and dose) for which booster doses may be preferred Rationale
  • Moderna Spikevax BA.1 Bivalent (50 mcg) and Pfizer-BioNTech Comirnaty BA.4/5 Bivalent (30 mcg) are authorized by Health Canada as booster doses in individuals ≥18 and ≥12 years of age, respectively.
  • Data to date indicates that bivalent Omicron-containing mRNA COVID-19 vaccines elicit higher neutralizing antibody responses against the original SARS-CoV-2 strain, Omicron BA.1 and Omicron BA.4 and BA.5 compared to original mRNA vaccines, when given as booster doses. However, the clinical relevance of these differences in antibody responses is unclear at this time.
  • Data to date also indicates that bivalent Omicron-containing mRNA COVID-19 vaccines have a similar safety profile to original mRNA COVID-19 vaccines.
  • Groups at high risk for severe outcomes from COVID-19 are likely to realize the greatest benefits from a fall COVID-19 booster dose.
  • Maximizing the benefit of protection of a booster dose may be affected by the interval between doses. A longer time between doses may result in a better response after any subsequent dose, as this allows time for the immune response to mature in breadth and strength. A longer interval may, however, also increase the chance of a period with waning (lower) protection while awaiting a next dose.
  • It was previously recommended that Pfizer-BioNTech Comirnaty original (30 mcg) may be preferred to Moderna Spikevax original (50 mcg) as a booster dose in adults 18-29 years of age but this recommendation has since been removed. This recommendation was issued based on precautionary principles, in the absence of direct evidence, informed by the observed product-specific difference in risks of myocarditis and/or pericarditis after the primary series. Evidence of the risks of myocarditis and/or pericarditis following a booster dose was limited at the time and not available in all populations.
  • Post-market safety surveillance data to date indicate that the risk of myocarditis following a booster dose is lower compared to that following the second dose in the primary series, and current data do not show a product-specific difference in the risks of myocarditis and/or pericarditis after a booster dose of an mRNA COVID-19 vaccine. Adults 18 to 29 years of age can receive a booster dose with any available bivalent Omicron-containing mRNA COVID-19 vaccine for which they are currently eligible.
  • Adolescents 12 to 17 years of age who are at increased risk of severe illness from COVID-19 (including those who are immunocompromised and who received a 3-dose primary series)
  • Moderna Spikevax BA.1 Bivalent (50 mcg) and Pfizer-BioNTech Comirnaty BA.4/5 Bivalent (30 mcg) are authorized by Health Canada as booster doses in individuals ≥18 and ≥12 years of age, respectively.
  • In moderately to severely immunocompromised adolescents 12-17 years of age, Moderna Spikevax BA.1 Bivalent (50 mcg) may be considered based on clinical discretion as Moderna Spikevax BA.1 Bivalent (50 mcg) may induce a greater immune response compared to Pfizer-BioNTech Comirnaty BA.4/5 Bivalent (30 mcg). The use of Moderna Spikevax Bivalent (50 mcg) in this age group represents an off-label recommendation and is informed by expert opinion.
  • There are currently no data on the efficacy, immunogenicity or safety of bivalent Omicron-containing mRNA COVID-19 vaccines in individuals <18 years of age.
  • All other adolescents 12 to 17 years of age
  • Children 5 to 11 years of age with an underlying medical condition that places them at high risk of severe illness due to COVID-19 (including those who are immunocompromised and who received a 3-dose primary series)
  • Pfizer-BioNTech Comirnaty (10 mcg) COVID-19 vaccine should be offered.
  • Pfizer-BioNTech Comirnaty original (10 mcg) is authorized by Health Canada as a booster dose in individuals 5 to 11 years of age.
  • No other COVID-19 vaccines are currently authorized or recommended for use as booster doses in this age group.
  • There is limited evidence on clinical risk factors for severe COVID-19 disease in pediatric populations.
  • For all other children 5 to 11 years of age
  • Pfizer-BioNTech Comirnaty (10 mcg) COVID-19 vaccine may be offered in the context of heightened epidemiological risk.
Table 3 Footnote a

For booster doses for adults 18 years of age and older who are not able or willing to receive an mRNA COVID-19 vaccine, a protein subunit COVID-19 vaccine (Novavax Nuvaxovid) may be offered to adults without contraindications to the vaccine. Novavax Nuvaxovid is not currently authorized for use as a booster dose in Canada, however clinical studies have been conducted. Janssen Jcovden COVID-19 vaccine may be offered as a first booster to individuals 18 years of age and older without contraindications to the vaccine only when all other COVID-19 vaccines are contraindicated. Medicago Covifenz is not currently authorized for use as a booster dose in Canada.

Table 3 Return to footnote a referrer

Table 3 Footnote b

For individuals in authorized age groups who are not able or willing to receive a bivalent Omicron-containing mRNA COVID-19 vaccine, an original mRNA COVID-19 vaccine may be offered.

Table 3 Return to footnote b referrer

Table 3 Footnote c

Pfizer-BioNTech Comirnaty BA.4/5 Bivalent (30 mcg) is authorized in individuals ≥12 years of age. Moderna Spikevax BA.1 Bivalent (50 mcg) is authorized in individuals ≥18 years of age.

Table 3 Return to footnote c referrer

Vaccination of specific populations

Pregnancy and breastfeeding

Compared to non-pregnant persons, SARS-CoV-2 infection in pregnancy is associated with increased risk of hospitalization and admission to an intensive care unit (ICU). SARS-CoV-2 infection during pregnancy is also associated with an increased risk in the neonate of preterm birth, low birth weight and admission to a neonatal intensive care unit (NICU).

Recommendations

It is recommended that a complete vaccine series with an mRNA COVID-19 vaccine should be offered to individuals in the authorized age group who are pregnant or breastfeeding. An mRNA vaccine is preferred due to reassuring published data on the safety of these vaccines in pregnancy.

It is recommended that an authorized protein subunit COVID-19 vaccine (Novavax Nuvaxovid) or VLP COVID-19 vaccine (Medicago Covifenz) may be offered to individuals in the authorized age group without contraindications to the vaccine who are not able or willing to receive an mRNA COVID-19 vaccine. Safety and efficacy data in individuals who are pregnant or breastfeeding following vaccination with a protein subunit COVID-19 vaccine or a VLP COVID-19 vaccine are not available.

A viral vector COVID-19 vaccine may be offered to individuals in the authorized age group who are pregnant or breastfeeding when all other authorized COVID-19 vaccines are contraindicated.

For booster doses, persons who are pregnant or breastfeeding are included among those for whom they are recommended. A recommended booster dose should be offered at any stage of pregnancy (i.e., in any trimester), regardless of the number of booster doses previously received. COVID-19 vaccine booster doses may be offered at an interval of 6 months since previous COVID-19 vaccine dose or SARS-CoV-2 infection. However, a shorter interval of at least 3 months may be warranted to optimize protection for the pregnant person in the context of heightened epidemiological risk (including increased risk of severe outcomes).

An individual may receive all doses for which they are eligible during the course of a pregnancy.

Considerations

Pregnant or breastfeeding individuals were excluded from the mRNA and viral vector COVID-19 vaccine clinical trials. However, analysis of data collected through international COVID-19 immunization registries to date have not revealed any maternal or neonatal safety signals. Most real-world evidence is for mRNA vaccination.

Those who are trying to become pregnant do not need to avoid pregnancy after vaccination with an mRNA vaccine.

No safety signals have been detected with mRNA vaccination during breastfeeding and individuals should continue to breastfeed after vaccination. People who are breastfeeding experience the same rates of side effects as do those who are not breastfeeding, and studies have not found any impacts of mRNA COVID-19 vaccination on the infant/child being fed human milk or on milk production or excretion.

Evidence suggests that COVID-19 mRNA vaccination during pregnancy results in comparable antibody titres to those generated in non-pregnant women. Maternal IgG humoral response to mRNA COVID-19 vaccines transfers across the placenta to the fetus, leading to a significant and potentially protective, antibody titre in the neonatal bloodstream 1 week after the second dose. Observational studies consistently show that both anti-spike IgG and IgA are present in breastmilk for at least 6 weeks after maternal vaccination with mRNA vaccines.

The safety and efficacy of Novavax Nuvaxovid and Medicago Covifenz have not been established in individuals who are pregnant or breastfeeding. Informed consent should include discussion that there is currently limited evidence on the use of the Novavax Nuvaxovid and Medicago Covifenz vaccines in individuals who are pregnant or breastfeeding, while there is evidence on the safety profile and effectiveness of mRNA COVID-19 vaccines in these populations based on real world use with large numbers of individuals.

Pregnant persons vaccinated with an mRNA COVID-19 vaccine during pregnancy experience the same rates of expected local and systemic adverse events as non-pregnant persons. Vaccination during pregnancy does not increase risk for miscarriage, stillbirth, low birth weight, preterm birth, NICU admission, or other adverse pregnancy/birth outcomes.

COVID-19 vaccines may be administered concurrently with (i.e., same day), or at any time before or after other vaccines recommended during pregnancy or while breastfeeding. Refer to Administration practices, Pre-vaccination counselling and Safety and adverse events for further information.

Vaccine recipients and health care providers are encouraged to enroll patients who have received a COVID-19 vaccine during pregnancy in COVID-19 vaccine pregnancy registries (see Table 4).

There is a Canadian COVID-19 Vaccine Registry for Pregnant and Lactating Individuals.

Table 4: Pregnancy registry information by vaccine product
Vaccine product Registry information
Pfizer-BioNTech Comirnaty COVID-19 vaccine Pfizer does not have a pregnancy exposure registry. Pfizer COVID-19 vaccine recipients and health care providers are encouraged to report any exposure to COVID-19 vaccine during pregnancy or breastfeeding to the vaccine manufacturer (1-866-723-7111).
Moderna Spikevax COVID-19 vaccines There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to the Moderna COVID-19 vaccine during pregnancy. Women who are vaccinated with the Moderna COVID-19 vaccine during pregnancy are encouraged to enroll in the registry by calling 1-866-MODERNA (1-866-663-3762).
AstraZeneca Vaxzevria COVID-19 vaccine There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to AstraZeneca COVID-19 vaccine during pregnancy. Women who are vaccinated with AstraZeneca COVID-19 vaccine during pregnancy are encouraged to enroll in the registry by visiting C-VIPER: COVID-19 Vaccines International Pregnancy Exposure Registry or calling 1-800-616-3791.
Janssen Jcovden COVID-19 vaccine There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to Janssen Jcovden COVID-19 vaccine during pregnancy. Women who are vaccinated with Janssen Jcovden COVID-19 vaccine during pregnancy are encouraged to enroll in the registry by visiting C-VIPER: COVID-19 Vaccines International Pregnancy Exposure Registry.

Refer to Immunization in Pregnancy and Breastfeeding in Part 3 for additional general information.

Individuals previously infected with SARS-CoV-2

A complete primary series may be offered in light of the variability in the robustness and durability of protection conferred by prior SARS-CoV-2 infection. The immune response due to prior infection may vary due to factors such as the severity of infection, age, presence of comorbidities and possibly the SARS-CoV-2 variant causing the infection.

Recommendations

It is recommended that mRNA COVID-19 vaccines should be offered to individuals 6 months of age and older with previous SARS-CoV-2 infection without contraindications to the vaccine.

It is recommended that an authorized protein subunit COVID-19 vaccine (Novavax Nuvaxovid) or VLP COVID-19 vaccine (Medicago Covifenz) may be offered to individuals in the authorized age group without contraindications to the vaccine who are not able or willing to receive an mRNA COVID-19 vaccine. Safety and efficacy data in individuals previously infected with SARS-CoV-2 following vaccination with a protein subunit COVID-19 vaccine or a VLP COVID-19 vaccine are not available.

Recommendations for booster doses also apply to individuals with previous SARS-CoV-2 infection.

Refer to Table 5 for suggested intervals between previous infection and COVID-19 vaccination prior to and after completion of the primary series. Refer to Booster doses for information regarding the type and dose of booster doses for individuals 5 years of age and older.

Table 5. Suggested intervals between previous SARS-CoV-2 infectionTable 5 Footnote a and COVID-19 vaccination
SARS-CoV-2 infectionTable 5 Footnote a timing relative to COVID-19 vaccination Population Suggested interval between SARS-CoV-2 infectionTable 5 Footnote a and vaccination (clinical discretion is advised)Table 5 Footnote bTable 5 Footnote c
Infection prior to completion or initiationTable 5 Footnote c of primary vaccination series Individuals 6 months of age and older who are not considered moderately to severely immunocompromised and with no history of MIS-C or MIS-A following vaccination Receive the vaccine 8 weeks after symptom onset or positive test (if asymptomatic)Table 5 Footnote b
Individuals 6 months of age and older who are moderately to severely immunocompromised and with no history of MIS-C or MIS-A following vaccination Receive the vaccine dose 4 to 8 weeks after symptom onset or positive test (if asymptomatic)Table 5 Footnote b
Individuals 6 months of age and older with a history of MIS-C or MIS-A following vaccination (regardless of immunocompromised status) Receive the vaccine dose when clinical recovery has been achieved or ≥90 days since diagnosis of MIS-C or MIS-A, whichever is longer
Infection after primary seriesTable 5 Footnote d but before a booster dose Individuals 5 years of age and older currently eligible for a booster dose 6 months since previous infection unless a shorter interval of 3 to <6 months is warranted in the context of heightened epidemiological riskTable 5 Footnote b
Table 5 Footnote a

Previous infection can be defined in different ways based on jurisdictional policies and access to testing. The following suggestion can be considered to define previous infection with SARS-CoV-2:

  • Confirmed by a molecular (e.g., PCR) or Health Canada-approved antigen detection-based test; or
  • Symptomatic disease compatible with COVID-19 AND household exposure to a confirmed COVID-19 case.

Table 5 Return to footnote a referrer

Table 5 Footnote b

These suggested intervals are based on immunological principles and expert opinion, and may change as evidence on COVID-19, variants of concern (VOCs), and COVID-19 vaccines emerge. When considering whether or not to administer vaccine doses following the suggested intervals outlined in this table, biological and social risk factors for exposure (e.g., local epidemiology, circulation of VOCs, living settings) and severe disease should also be taken into account. These intervals are a guide and clinical discretion is advised.

Table 5 Return to footnote b referrer

Table 5 Footnote c

For individuals who have not had any previous doses, they may receive their first dose after acute symptoms of COVID-19 have resolved and they are no longer infectious, or they may follow these suggested intervals. Individual benefit/risk assessment and clinical discretion are advised as per footnote "b". These suggested waiting times are intended to minimize the risk of transmission of COVID-19 at an immunization venue and to enable monitoring for COVID-19 vaccine adverse events without potential confounding from symptoms of COVID-19 or other co-existing illnesses.

Table 5 Return to footnote c referrer

Table 5 Footnote d

The primary series is outlined in Recommendations for use. Note that for moderately to severely immunocompromised individuals who were immunized with a primary series that includes one additional dose, a booster dose would be subsequent to that additional dose.

Table 5 Return to footnote d referrer

Considerations

Testing for previous SARS-CoV-2 infection is not needed prior to COVID-19 vaccination.

A longer interval between infection and vaccination may result in a better immune response as this allows time for this response to mature in breadth and strength, and for circulating antibodies to decrease, thus avoiding immune interference when the vaccine is administered.

Current evidence (prior to Omicron) suggests protection is more robust and longer lasting with vaccination in previously infected individuals compared to immunity from SARS-CoV-2 infection alone.

COVID-19 vaccination in individuals previously infected with SARS-CoV-2 has a good safety profile and is well tolerated. Limited evidence suggests reactogenicity may be slightly increased in individuals previously infected with SARS-CoV-2 compared to those with no history of previous infection, however this evidence is limited to the primary series and variants prior to Omicron.

Vaccination of SARS-CoV-2 naïve individuals with COVID-19 vaccines has not been reported to elicit enhanced or altered disease upon subsequent infection by SARS-CoV-2 (e.g., vaccine-enhanced disease).

The safety and efficacy of Novavax Nuvaxovid and Medicago Covifenz have not been established in individuals previously infected with SARS-CoV-2. Informed consent should include discussion that there is currently limited evidence on the use of the Novavax Nuvaxovid and Medicago Covifenz vaccines in individuals previously infected with SARS-CoV-2, while there is evidence on the safety profile and effectiveness of mRNA COVID-19 vaccines in this population based on real world use with large numbers of individuals.

Persons with an autoimmune condition

Recommendations

It is recommended that an mRNA COVID-19 vaccine should be preferentially offered to complete the vaccine series in individuals in the authorized age group with an autoimmune condition.

It is recommended that an authorized protein subunit COVID-19 vaccine (Novavax Nuvaxovid) or VLP COVID-19 vaccine (Medicago Covifenz) may be offered to individuals in the authorized age group without contraindications to the vaccine who are not able or willing to receive an mRNA COVID-19 vaccine. Safety and efficacy data in persons with an autoimmune condition following vaccination with a protein subunit COVID-19 vaccine or a VLP COVID-19 vaccine are not available.

A viral vector COVID-19 vaccine may be offered to individuals in the authorized age group with an autoimmune condition only when all other authorized COVID-19 vaccines are contraindicated. Safety data in these populations following vaccination with a viral vector vaccine are not available.

Considerations

Although participants with autoimmune conditions who were not immunosuppressed were not excluded from trials, they constitute a very small proportion of trial participants and represent a very narrow range of autoimmune conditions. However, real-world evidence (mostly with mRNA vaccination) has become available.

Observational studies in individuals with autoimmune conditions indicate that the frequency and severity of adverse events in this population is comparable to that of individuals without autoimmune conditions and what was reported in clinical trials. The onset of new autoimmune disease or disease exacerbation following vaccination with mRNA COVID-19 vaccines was rare or comparable to the background incidence of these events in the general population.

The safety and efficacy of Novavax Nuvaxovid and Medicago Covifenz have not been established in individuals who have an autoimmune condition. Informed consent should include discussion that there is currently limited evidence on the use of the Novavax Nuvaxovid and Medicago Covifenz vaccines in persons with an autoimmune condition, while there is evidence on the safety profile and effectiveness of mRNA COVID-19 vaccines in this population based on real world use with large numbers of individuals.

Refer to Immunization of persons with chronic diseases in Part 3 for additional general information on autoimmune conditions.

Immunocompromised persons

Recommendations

It is recommended that children 6 months to 11 years of age who are moderately to severely immunocompromised should be immunized with a primary series of 3 doses of an mRNA COVID-19 vaccine authorized for their age, using an interval of 4 to 8 weeks between each dose. For those children aged 6 months to 11 years who are moderately to severely immunocompromised who have previously received a 2-dose series with an mRNA COVID-19 vaccine, it is recommended that a third dose should be offered 4 to 8 weeks after the second dose.

For individuals 12 years of age and older who are moderately to severely immunocompromised and have not yet been immunized, it is recommended that a primary series of 3 doses of an mRNA vaccine should be offered. For those who are moderately to severely immunocompromised who have previously received a 1- or 2-dose COVID-19 vaccine series (with a homologous or heterologous schedule using mRNA or viral vector vaccines as per authorized age groups), it is recommended that an additional dose of an mRNA COVID-19 vaccine should be offered.

Indirect data from adult populations (≥18 years of age) suggest Moderna Spikevax original (100 mcg) may result in higher vaccine effectiveness after a 2-dose primary series compared to Pfizer-BioNTech Comirnaty original (30 mcg) and is associated with a higher seroconversion rate among adult immunocompromised patients. Given this potential benefit, for some immunocompromised individuals 6 to 11 years of age, administration of the Moderna Spikevax original (50 mcg) vaccine as a 3-dose primary series may be considered and for some immunocompromised individuals aged 12 to 29 years, the Moderna Spikevax original (100 mcg) vaccine as a 3-dose primary series may be considered (based on clinical judgement).

mRNA COVID-19 vaccines are preferred and are authorized for a 3-dose primary series in moderately to severely immunocompromised individuals. Based on clinical discretion, a protein subunit COVID-19 vaccine (Novavax Nuvaxovid) or VLP COVID-19 vaccine (Medicago Covifenz) may be offered to moderately to severely immunocompromised individuals in the authorized age group without contraindications to the vaccine who are not able or willing to receive an mRNA COVID-19 vaccine. However, neither the protein subunit COVID-19 vaccine (Novavax Nuvaxovid) nor the VLP COVID-19 vaccine (Medicago Covifenz) is currently authorized as a 3-dose primary series in these populations and safety and efficacy data in immunocompromised persons following vaccination with a protein subunit COVID-19 vaccine or a VLP COVID-19 vaccine are not available.

A viral vector COVID-19 vaccine may be offered to individuals in the authorized age group who are immunosuppressed due to disease or treatment only when all other authorized COVID-19 vaccines are contraindicated.

Note that for moderately to severely immunocompromised individuals who were immunized with a primary series that includes one additional dose, all booster doses would be subsequent to that additional dose.

Refer to Booster doses for information regarding booster doses for moderately to severely immunocompromised adults 5 years of age and older.

Considerations

Immunocompromised individuals, including those receiving immunosuppressive therapy, are at increased risk for prolonged infection and serious complications from SARS-CoV-2 infection. Numerous studies have shown that immunogenicity is substantially decreased in some immunocompromised individuals when compared to healthy vaccine recipients, although evidence is limited to studies in adolescent and adult populations. Observational studies in adults with complete 1 or 2 dose series, show a reduction in vaccine effectiveness against SARS-CoV-2 infection and COVID-19 disease in immunocompromised adults when compared to the general population.

The minimal interval between the initial doses of the primary series and the additional dose should be 28 days. An interval longer than the minimum 28 days between doses is likely to result in a better immune response. However, moderately to severely immunocompromised individuals (after the initial 1- or 2- doses of the primary series) may still be susceptible during this time before the next dose is administered. If a longer interval between doses is being considered, then the need for earlier protection due to risk of exposure (including local transmission of SARS-CoV-2, circulation of VOC) and risk of severe disease (e.g., underlying high risk medical condition) should be taken into account.

A vaccine series should ideally be completed at least 2 weeks before initiation of immunosuppressive therapies where possible.

Moderately to severely immunocompromised includes individuals with the following conditions:

A range of factors can impact the relative degree of immunocompromise and response to COVID-19 vaccines, and clinical and public health judgement should be applied. Jurisdictions may modify the list based on population considerations.

Refer to Immunization of Immunocompromised Persons in Part 3 for a suggested definition of high dose steroids and for guidance on vaccination with COVID-19 vaccines for individuals pre- and post-hematopoietic stem cell transplantation (HSCT) and for chimeric antigen receptor (CAR) T cell therapy recipients.

The safety and efficacy of Novavax Nuvaxovid and Medicago Covifenz have not been established in individuals who are immunocompromised due to disease or treatment. Informed consent for use of either vaccine in these populations should include discussion that there is currently limited evidence on the use of Novavax Nuvaxovid and Medicago Covifenz in these populations, while there is evidence on the safety profile and effectiveness of mRNA COVID-19 vaccines in these populations based on real world use with large numbers of individuals.

Evidence indicates that humoral immune responses increase in some individuals after a third dose of mRNA COVID-19 vaccine is administered to adults with immunocompromising conditions, although the degree of increase varies between studies and according to the type of immunocompromising condition or treatment.

Studies assessing additional doses in immunocompromised individuals have primarily used mRNA vaccines, for both the initial primary series and additional dose, and are limited to studies in adult populations. Moderna Spikevax original and bivalent COVID-19 vaccine may produce a greater immune response in this population. Investigations are ongoing.

Based on observational studies the frequency and severity of AEFIs with an mRNA COVID-19 vaccine in certain immunocompromised populations were comparable to that of non-immunosuppressed individuals. No worsening of underlying disease was reported after immunization.

In observational studies and clinical trials, humoral and cellular immune responses were similar between fully vaccinated people living with HIV on antiretroviral therapy and those who were HIV-negative.

Refer to Immunization of Immunocompromised Persons in Part 3 for definitions and additional general information.

Travellers

Travellers should receive a complete series of COVID-19 vaccine at least 2 weeks prior to departure. Two weeks or more may be required to meet entry requirements for other countries. Travellers should verify the travel requirements in place at their destination(s) and for their return to Canada. For more information, refer to the Committee to Advise on Tropical Medicine and Travel (CATMAT) Statement on COVID-19 and International Travel.

Persons new to Canada

Based on a recommendation by PHAC to provinces and territories, people who are planning to live, work or study in Canada who have had only a complete or incomplete primary series of non-Health Canada authorized vaccines, should be offered an additional dose of an mRNA vaccine, unless they have already received 3 doses of a COVID-19 vaccine. They should receive booster doses when eligible.

Serologic testing

Serologic testing is not needed before or after immunization with COVID-19 vaccine.

Administration practices

Dose and route of administration

Dose

Pfizer-BioNTech Comirnaty COVID-19 original vaccine (30 mcg)

There are two original formulations of Comirnaty authorized for use in individuals 12 years of age and older.

The dose for the Pfizer-BioNTech Comirnaty COVID-19 vaccine (0.3 mL) is unique compared to that of most routine vaccinations. Special precaution should be taken to ensure the correct dose is taken from the multi-dose vial.

Pfizer-BioNTech Comirnaty COVID-19 original vaccine (10 mcg, pediatric formulation)

This formulation has an orange vial cap and orange label border and is authorized for use in those 5 to 11 years of age.

Dilute with 1.3 mL 0.9% Sodium Chloride Injection, USP prior to use.

Each dose is 0.2 mL after dilution, containing 10 mcg of SARS-CoV-2 spike protein mRNA.

The dose for the Pfizer-BioNTech Comirnaty COVID-19 vaccine pediatric formulation (0.2 mL) is unique compared to that of most routine vaccinations. Special precaution should be taken to ensure the correct dose is taken from the multi-dose vial.

Pfizer-BioNTech Comirnaty Original & Omicron BA.4/BA.5 COVID-19 vaccine (Bivalent)

This formulation has a gray vial cap and gray label border and is authorized for use in those 12 years of age and older.

No dilution is required.

Each dose is 0.3 mL, containing 30 mcg (15 mcg each of mRNA encoding for the original SARS-CoV-2 virus and the Omicron BA.4/BA.5 variant).

Moderna Spikevax original COVID-19 vaccine

There are two formulations of Moderna Spikevax original authorized for use in individuals 6 months of age and older.

The volume (mL) required for primary series and booster dosing will be different depending on which presentation of the vaccine is being administered. Careful attention should be paid to the vial and carton label, vial cap colour, label border colour and corresponding dose volumes.

Moderna Spikevax Bivalent COVID-19 vaccine

Each dose is 0.5 mL, containing 50 mcg (25 mcg original SARS-CoV-2 + 25 mcg Omicron BA.1).

Vials have a royal blue cap and a green label border and contain 0.10 mg/mL in a 2.5 mL multidose vial.

No dilution is required.

Table 6. Dosing for Moderna Spikevax vaccines
Presentation Cap/label colour Age Vaccination Dose Dose volume
Original
0.2 mg/mL
Multidose vial 5 mL
Red cap/light blue label border 12+ years primary series 100 mcgTable 6 Footnote a 0.5 mL
booster 50 mcgTable 6 Footnote b 0.25 mL
6-11 years primary series 50 mcg 0.25 mL
Original
0.1 mg/mL
Multidose vial 2.5 mL
Royal blue cap/purple label border 12+ years booster 50 mcgTable 6 Footnote b 0.5 mL
6-11 years primary series 50 mcg 0.5 mL
6 months – 5 years primary series 25 mcgTable 6 Footnote c 0.25 mL
Bivalent
0.1 mg/mL
Multidose vial 2.5 mL
Royal blue cap/green label border 18 years + booster 50 mcg 0.5 mL
Table 6 Footnote a

The 0.10 mg/mL presentation is not intended for preparation of the 100 mcg dose.

Table 6 Return to footnote a referrer

Table 6 Footnote b

Some populations may receive a 100 mcg booster dose.

Table 6 Return to footnote b referrer

Table 6 Footnote c

The 0.20 mg/mL presentation is not intended for preparation of the 25 mcg dose.

Table 6 Return to footnote c referrer

Refer to Booster doses for additional information.

Novavax Nuvaxovid COVID-19 vaccine

Each dose is 0.5 mL, containing 5 mcg SARS-CoV-2 recombinant spike protein.

No dilution is required.

Medicago Covifenz COVID-19 vaccine

Each dose is 0.5 mL, containing 3.75 mcg SARS-CoV-2 recombinant spike protein.

The antigen component of Covifenz is a suspension, which must be mixed 1:1 with the AS03 adjuvant emulsion component prior to administration.

AstraZeneca Vaxzevria COVID-19 vaccine

Each dose is 0.5 mL, containing 5 x 1010 particles of SARS-CoV-2 spike protein.

No dilution is required.

Janssen Jcovden COVID-19 vaccine

Each dose is 0.5 mL, containing 5 x 1010 particles of SARS-CoV-2 spike protein.

No dilution is required.

Route of administration

COVID-19 vaccines are given as an intramuscular (IM) injection. The deltoid muscle of the arm is the preferred injection site in adolescents and adults, unless the muscle mass is not adequate or vaccination in that site is not possible, in which case the anterolateral thigh can be used.

Refer to Vaccine Administration Practices in Part 1 for additional general information.

If an error in vaccine administration occurs, refer to Managing COVID-19 vaccine administration errors or deviations for guidance.

Interchangeability of vaccines

Regardless of which product is offered, the previous dose should be counted, and the series need not be restarted.

mRNA COVID-19 vaccines

If readily available (i.e., easily available at the time of vaccination without delay or vaccine wastage), the same mRNA COVID-19 vaccine product should be offered for the subsequent dose in a vaccine series started with an mRNA COVID-19 vaccine. However, when the same mRNA COVID-19 vaccine product is not readily available, or is unknown, another mRNA COVID-19 vaccine product recommended for use in that age group can be considered interchangeable and should be offered to complete the vaccine series.

There are currently no data on the use of bivalent Omicron-containing mRNA COVID-19 vaccines as part of a primary series. A primary series with an original mRNA vaccine is recommended in all authorized age groups.

Novavax Nuvaxovid COVID-19 vaccine

Novavax Nuvaxovid may be used to start or complete a primary series, or used as a booster dose in a mixed prime-boost series, for individuals for whom mRNA COVID-19 vaccine is contraindicated, inaccessible, or has been refused.

Informed consent should include a discussion of the benefits and risks given the limited data available on mixed schedules with Novavax Nuvaxovid, and that this vaccine is not currently authorized for use as a booster dose in Canada. There is currently no data on the use of Novavax Nuvaxovid in a mixed series with Moderna Spikevax original (100 mcg) or Janssen Jcovden COVID-19 vaccines.

Medicago Covifenz COVID-19 vaccine

Medicago Covifenz has not yet been evaluated in a heterologous (mixed) primary series.

Mixed schedules using Medicago Covifenz specifically and other COVID-19 vaccines, have not been studied. Available evidence for other COVID-19 vaccine products indicates that mixed schedules have acceptable safety profiles.

Informed consent should include a discussion of the benefits and risks given the absence of data available on mixed schedules with Medicago Covifenz.

AstraZeneca Vaxzevria COVID-19 vaccine

While an AstraZeneca Vaxzevria COVID-19 vaccine, an mRNA COVID-19 vaccine, or Novavax Nuvaxovid COVID-19 vaccine product may be offered for the subsequent dose in a primary vaccine series started with an AstraZeneca Vaxzevria COVID-19 vaccine, an mRNA COVID-19 product is preferred as a subsequent dose.

Mixed COVID-19 vaccine schedules

For mixed COVID-19 vaccine schedules, the minimum interval between doses should be based on the minimum interval of the product used for the first dose (e.g., mRNA vaccine should be offered a minimum of 28 days after AstraZeneca Vaxzevria COVID-19 vaccine as this is the minimum interval for AstraZeneca Vaxzevria). When using mixed schedules, the suggested optimal interval between doses is 8 weeks based on considerations following Table 2.

Evidence indicates that mixed COVID-19 viral vector and mRNA vaccine schedules with dosing intervals between 4 and 12 weeks have acceptable safety profiles that may be associated with increased short-term systemic reactogenicity, which is potentially increased with shorter intervals between vaccines.

Limited evidence indicates that mixed COVID-19 original vaccine schedules where Novavax Nuvaxovid is administered after a partial or complete primary series of AstraZeneca Vaxzevria or Pfizer-BioNTech Comirnaty orginal COVID-19 vaccines has an acceptable safety profile and is immunogenic, although may not be as immunogenic compared to the Pfizer-BioNTech Comirnaty original or Moderna Spikevax original vaccines.

Concurrent administration with other vaccines

With the exception of Moderna Spikevax original (25 mcg) for those 6 months to 5 years of age, COVID-19 vaccines may be given concurrently with (i.e., same day), or at any time before or after, non-COVID-19 vaccines (including live and non-live vaccines).

As Moderna Spikevax original (25 mcg) is a newly authorized vaccine in the 6 months to 5 years of age group, evidence relating to any risk of rare or very rare adverse events (AEs) will be monitored. It is advised to wait 14 days between vaccine products when administering the Moderna Spikevax original (25 mcg) COVID-19 vaccine and other vaccines. This could prevent erroneous attribution of an AE to one particular vaccine or the other. Concurrent administration or a shortened interval between the Moderna Spikevax original (25 mcg) COVID-19 vaccine and other vaccines may be warranted on an individual basis in some circumstances at the clinical discretion of the healthcare provider.

If more than one type of vaccine is administered at a single visit, they should be administered at different injection sites using separate injection equipment.

Informed consent should include a discussion of the benefits and risks given the limited data available on administration of COVID-19 vaccines at the same time as, or shortly before or after, other vaccines.

There are currently limited data available on whether the reactogenicity of COVID-19 vaccines is increased with concurrent administration of other vaccines. No specific safety concerns have been identified to date. Studies to assess the safety and immunogenicity of concurrent administration of COVID-19 vaccines with other vaccines are ongoing.

Refer to Timing of Vaccine Administration in Part 1 for additional general information on concurrent administration of other vaccines.

Pre-vaccination counselling

Prophylactic oral analgesics or antipyretics (e.g., acetaminophen or ibuprofen) should not be routinely used before or at the time of vaccination, but their use is not a contraindication to vaccination. There is currently no evidence of benefit from administration of oral analgesics for the prevention of immunization injection pain or systemic reactions.

Prior to providing a COVID-19 vaccine, informed consent should include discussion about frequently occurring minor adverse events and the risks and symptoms of potential rare severe adverse events.

Anyone receiving any viral vector COVID-19 vaccine (AstraZeneca Vaxzevria or Janssen Jcovden) should be informed of the risks associated with viral vector vaccines: Guillain-Barré syndrome (GBS), thrombosis with thrombocytopenia syndrome (TTS) including VITT, capillary leak syndrome (CLS), venous thromboembolism (VTE), immune thrombocytopenia (ITP) and anaphylaxis, and be advised to seek medical attention if they develop signs and symptoms suggestive of these conditions.

Anyone receiving any mRNA COVID-19 vaccine (Pfizer-BioNTech Comirnaty original, Pfizer-BioNTech Comirnaty Original & Omicron BA.4/BA.5 (bivalent), Moderna Spikevax original or Moderna Spikevax Bivalent) should be informed of the risks associated with mRNA COVID-19 vaccines: myocarditis/pericarditis, Bell's palsy and anaphylaxis, and be advised to seek medical attention if they develop signs and symptoms suggestive of these conditions.

Refer to Safety and adverse events for further information.

Post-vaccination counselling

Oral analgesics or antipyretics may be considered for the management of adverse events (e.g., pain or fever, respectively), if they occur after vaccination. Analgesics and antipyretics were used in clinical trials of COVID-19 vaccines for the management of pain and/or fever after vaccination.

All vaccine recipients should be instructed to seek medical care if they develop signs or symptoms of a serious adverse event or an allergic reaction following vaccination.

Refer to Vaccine Administration Practices in Part 1 for additional information on pre- and post-vaccination counseling.

Storage requirements

For information on storage, handling and transport of frozen and thawed vaccine vials, refer to the Overview of key features of COVID-19 vaccines authorized in Canada.

For additional information, consult the product leaflet or information contained within the product monograph available through Health Canada's Drug Product Database. Refer to Storage and Handling of Immunizing Agents in Part 1 for additional general information.

Safety and adverse events

Evidence on vaccine safety is available from COVID-19 clinical trials and ongoing international COVID-19 vaccine safety monitoring. The clinical trials solicited adverse events for defined lengths of time following a vaccine dose, as well as collecting unsolicited and serious events.

For reported side effects following COVID-19 vaccination in Canada, refer to the PHAC AEFI report.

Refer to Vaccine Safety and Pharmacovigilance and Adverse Events Following Immunization (AEFI) in Part 2 for additional information on vaccine safety and for definitions of AEFIs, and reporting of AEFI to public health.

Very common and common adverse events

Common adverse events are defined as those that occur in 1% to less than 10% of vaccine recipients; very common adverse events occur in 10% or more of vaccine recipients.

Local

Local adverse events were usually mild or moderate and resolved within a few days of vaccination. Pain at the injection site was very common. Redness and swelling were common or very common after administration of any authorized COVID-19 vaccine. Compared to adolescents and young adults, children aged 5 to 11 years or 6 to 11 years (Pfizer-BioNTech Comirnaty original or Moderna Spikevax original, respectively) had similar frequencies of pain at the injection site, however children 5 to 11 years of age that received Pfizer-BioNTech Comirnaty original had higher frequencies of swelling and redness. Localized axillary (or groin) swelling and tenderness (lymphadenopathy) was a solicited adverse event in the Moderna Spikevax original COVID-19 vaccine clinical trial and was very common after administration of that vaccine.

Systemic

Systemic adverse events were usually mild or moderate and resolved within a few days of vaccination. Fatigue, headache, muscle pain, chills, and joint pain were all either common or very common after the administration of any authorized COVID-19 vaccine. Relative to adolescents and young adults, systemic adverse events in children aged 5 to 11 years of age were comparable or less frequent for some events (such as fever and chills). However, fever was more frequently reported following dose 2 for the Moderna Spikevax original COVID-19 vaccine among children aged 6-11 years compared to adolescents.

For the Moderna Spikevax original (25mcg pediatric dose) clinical trial, the most frequently reported solicited local and systemic adverse reactions were irritability/crying, pain, sleepiness, and loss of appetite among participants 6 to 36 months of age. Fatigue (48.4%) was the most frequently reported systemic adverse reaction among participants 37 months to 5 years of age. Fever (≥38°C) was reported in 7.7% to 18.9% of participants 6 months to 5 years of age with fever >40.0°C being uncommon (≤0.3%).

Adverse events following the second dose of COVID-19 vaccine in individuals previously infected with SARS-CoV-2

COVID-19 vaccination in individuals previously infected with SARS-CoV-2 has a good safety profile and is well tolerated. Limited evidence suggests reactogenicity may be slightly increased in individuals previously infected with SARS-CoV-2 compared to those with no history of previous infection; however this evidence is limited to the primary series and infection with variants prior to Omicron.

Adverse events following bivalent Omicron- containing mRNA COVID-19 vaccines

Available clinical trial data show that Moderna Spikevax Bivalent (50 mcg) administered as a second booster dose to individuals ≥18 years of age had a similar reactogenicity profile to that of Moderna Spikevax original (50 mcg) given as a second booster dose. Post licensure surveillance is ongoing.

There are no clinical safety data currently available for Pfizer-BioNTech Comirnaty Original & Omicron BA.4/BA.5 (30 mcg) bivalent vaccine specifically; however, indirect data (clinical and post-market safety data) suggest that this vaccine will likely be well tolerated with a similar safety profile to Comirnaty original (30 mcg) and Comirnaty BA.1 Bivalent (30 mcg) vaccines, when used as a booster dose.

Uncommon, rare and very rare adverse events

Uncommon adverse events occur in 0.1% to less than 1% of vaccine recipients. Rare and very rare adverse events occur in 0.01% to less than 0.1% and less than 0.01% of vaccine recipients, respectively. The probability of detection of very rare adverse events in clinical trials is low given clinical trial sample sizes; therefore, ongoing pharmacovigilance is essential.

Lymphadenopathy

Lymphadenopathy was an unsolicited event that was uncommonly reported after administration of the Pfizer-BioNTech Comirnaty original (both 10 mcg and 30 mcg formulations), AstraZeneca Vaxzevria and Janssen Jcovden COVID-19 vaccines in clinical trials.

Myocarditis or pericarditis following vaccination with an mRNA COVID-19 vaccine

Rare cases of myocarditis (inflammation of the heart muscle) and/or pericarditis (inflammation of the lining around the heart) have been reported following vaccination with COVID-19 mRNA vaccines.

Cases following mRNA COVID-19 vaccination are consistently reported to have occurred:

Analyses of primary series surveillance data in Canada, US and European Nordic countries suggests a higher rate of myocarditis/pericarditis cases reported after vaccination with Moderna Spikevax original (100 mcg) compared to Pfizer-BioNTech Comirnaty original (30 mcg) vaccine especially among 12 to 29 year old males following a second dose of vaccine.

Myocarditis unrelated to exposure to COVID-19 disease or COVID-19 vaccines is typically less common in younger children 5 to 11 years of age. Safety surveillance data from the US suggests that the risk of myocarditis or pericarditis may be lower in children aged 5 to 11 years following Pfizer-BioNTech original (10 mcg) vaccination compared to adolescents and young adults (who receive a 30 mcg Pfizer-BioNTech original dose). Among children 5 to 11 years of age following vaccination with Pfizer-BioNTech Comirnaty original (10 mcg), very rare cases were most often reported following dose 2 and among males. Although the risk of myocarditis or pericarditis with Moderna Spikevax original (50 mcg) in children 6 to 11 years of age is unknown, the rare risk of myocarditis or pericarditis was higher with Moderna Spikevax original (100 mcg) than with Pfizer-BioNTech Comirnaty original (30 mcg) with a primary series in adolescents and young adults. Post-market safety surveillance is ongoing.

For children 6 months to 5 years of age, safety surveillance data from the US suggest that there is no increased risk of myocarditis following administration of Moderna Spikevax original (25 mcg) vaccine. As of August 21, 2022, no cases of myocarditis have been reported following administration of over 660,000 first or second doses of Moderna Spikevax (25 mcg) vaccine.

While long-term follow-up is ongoing, available data indicate that the majority of individuals who reported myocarditis/pericarditis after mRNA COVID-19 vaccination, though requiring hospitalization, have responded well to conservative therapy and tend to recover quickly.

Healthcare providers should consider myocarditis/pericarditis in their evaluation if the patient presents with clinically compatible symptoms (e.g., chest pain, shortness of breath, palpitations) after an mRNA COVID-19 vaccine regardless of timing from vaccination to symptoms onset. Investigations include electrocardiogram, serum troponins and echocardiogram. Frequent abnormal electrocardiogram findings and elevated troponin levels have been noted with myocarditis/pericarditis following mRNA vaccine.

Consultation with a cardiologist, infectious disease specialist, internal medicine specialist and/or rheumatologist may be advisable to assist in this evaluation, particularly to investigate the many potential causes of myocarditis and pericarditis. Investigations may include diagnostic testing for acute COVID-19 infection (e.g., PCR testing), prior SARS-CoV-2 infection and consideration of other potential infectious or non-infectious etiologies including auto-immune conditions.

Myocarditis/pericarditis following vaccination with other COVID-19 vaccines

Cases of myocarditis/pericarditis have been reported following the administration of Novavax Nuvaxovid including two teenage males who had myocarditis shortly after receiving a second dose of vaccine. In both individuals, clinical course was mild with complete resolution and no sequelae. The information currently available is insufficient to determine a causal relationship with the vaccine. Post-market safety surveillance is required to determine whether this is an adverse event of interest associated with Novavax Nuvaxovid.

Venous thromboembolism (VTE)

Venous thromboembolism (VTE) has been observed rarely following vaccination with the Janssen Jcovden COVID-19 Vaccine. In individuals with a pre-existing increased risk for thromboembolism, the possible increased risk of VTE with vaccine use should be considered.

Guillain-Barré syndrome (GBS) following vaccination with viral vector COVID-19 vaccines

Guillain-Barré syndrome (GBS) is a rare but potentially serious immune-mediated neurologic disorder that results in pain or numbness, muscle weakness, and paralysis in severe cases. Most people fully recover from GBS but some have residual deficits or symptoms and rarely, fatal cases can occur. To date, no increased risk of GBS has been identified following vaccination with the mRNA COVID-19 vaccines (Pfizer-BioNTech Comirnaty original and Moderna Spikevax original). Investigations have identified an increased risk of GBS following vaccination with the viral vector COVID-19 vaccines (AstraZeneca Vaxzevria and Janssen Jcovden). Among cases reported in Canada as of December 3rd 2021, symptoms occurred between 6 hours and 25 days after vaccination, the median age was 56 years (range 40 to 77 years old) and 26 (74%) were males.

The risk of GBS recurrence after COVID-19 vaccination amongst those with a past history of GBS appears to be low. Two cases have been described in the literature: 1 following Pfizer-BioNTech Comirnaty original (30 mcg) vaccine and 1 following a viral vector vaccine (product unknown). A causal association between these recurrences and COVID-19 vaccination has not been established. Both cases were recovering at the time of reporting.

Symptoms of GBS may include:

Bell's palsy following vaccination with an mRNA COVID-19 vaccine

Very rare cases of Bell's palsy (typically temporary weakness or paralysis on one side of the face) have been reported following vaccination with COVID-19 mRNA vaccines (Pfizer-BioNTech Comirnaty original or Moderna Spikevax original) in Canada and internationally among individuals aged 12 years and older. Bell's palsy is an episode of facial muscle weakness or paralysis. The condition is typically temporary. Symptoms appear suddenly and generally start to improve after a few weeks. The exact cause is unknown. It's believed to be the result of swelling and inflammation of the nerve that controls muscles on the face.

Symptoms of Bell's palsy may include:

Individuals should seek medical attention if they develop symptoms of Bell's palsy following receipt of mRNA COVID-19 vaccines. Healthcare providers should consider Bell's palsy in their evaluation if the patient presents with clinically compatible symptoms after an mRNA COVID-19 vaccine. Investigations should exclude other potential causes of facial paralysis.

Multisystem inflammatory syndrome in children or in adults (MIS-C or MIS-A) following vaccination with an mRNA COVID-19 vaccine

During the manufacturer-led clinical trials for mRNA COVID-19 vaccines, no cases of MIS-C were reported among children or adolescents. However, any rare or very rare AE that occurs at a frequency less often than 1 in 10,000 would likely not be detected due to the limitations of the trial size.

Very rare cases of MIS-C or MIS-A have been reported following vaccination with COVID-19 mRNA vaccines in Canada and internationally among individuals aged 12 years and older. In October, 2021, the European Medicines Agency (EMA) Pharmacovigilance Risk Assessment Committee (EMA-PRAC) issued a statement that there is currently insufficient evidence on a possible link between mRNA COVID-19 vaccines and very rare cases of MIS-C or MIS-A.

Severe immediate allergic reactions (e.g., anaphylaxis) following vaccination with COVID-19 vaccines

Anaphylaxis is a very rare, severe, life-threatening allergic reaction typically with a rapid onset that involves multiple organ systems and can progress rapidly. Symptoms and signs of anaphylaxis may include but are not limited to generalized urticaria; wheezing; swelling of the mouth, tongue, and throat; difficulty breathing; vomiting; diarrhea; hypotension; decreased level of consciousness; and shock.

Very rare cases of severe immediate allergic reactions (e.g., anaphylaxis) have been reported following vaccination with mRNA COVID-19 vaccines. Individuals tend to recover quickly with appropriate treatment and there have been no fatalities nor long-term morbidity observed with any of these severe immediate allergic reactions in Canada. Most of the reported cases have occurred within 30 minutes of vaccination.

Studies have shown that individuals with a severe immediate allergic reaction after a previous dose of mRNA vaccine can be re-vaccinated with the same vaccine or another mRNA COVID-19 vaccine following an appropriate medical assessment. In these studies, re-vaccination was safe and well tolerated with predominantly no, or mild, reactions after re-vaccination when provided in a controlled environment. Available evidence also suggests that most of the reported severe immediate allergic reactions following mRNA COVID-19 vaccines are likely not Immunoglobulin E (IgE)-mediated and therefore have a low risk of recurrence following future vaccine doses. Refer to Precautions below for additional information.

Refer to Anaphylaxis and other Acute Reactions Following Vaccination in Part 2 for information on the management of anaphylaxis post-vaccination.

Thrombosis with thrombocytopenia syndrome (TTS) following vaccination with viral vector COVID-19 vaccines

Very rare cases of serious blood clots or thrombosis (at unusual sites such as cerebral venous sinus thrombosis, splanchnic vein thrombosis, as well as arterial thrombosis) associated with thrombocytopenia have been reported following vaccination with viral vector COVID-19 vaccines. The terminology for this syndrome has been evolving. The Canadian Adverse Events Following Immunization Surveillance System (CAEFISS) uses the Brighton Collaboration case definition for TTS to detect these rare events. In Canada, TTS cases that test positive for a biomarker, anti-PF4 (antibodies to platelet factor 4-polyanion complexes), represent a subset of events and are being referred to as VITT.

The exact mechanism by which the viral vector COVID-19 vaccines trigger this syndrome is still under investigation. Viral vector vaccines appear to trigger a presentation similar to spontaneous heparin-induced thrombosis (HIT)/autoimmune heparin-induced thrombosis, where antibodies to platelet factor 4 (PF4)-polyanion complexes induce platelet activation, which causes thrombosis and thrombocytopenia. Clots related to VITT can be very aggressive and challenging to treat. Please refer to Thrombosis Canada guidance for clinical management of VITT. They cannot be managed the same way as clots related to oral contraceptives, immobility, or long-haul flights, and have an entirely different biologic pathophysiology.

Cases of TTS usually occur between 4 and 28 days after receipt of a viral vector COVID-19 vaccine, and patients should be monitored for symptoms up to 42 days. The rate of TTS after the first dose is estimated to be between 1 per 26,000 and 1 per 100,000 doses of AstraZeneca Vaxzevria COVID-19 vaccine administered and 1 per 300,000 doses of Janssen Jcovden COVID-19 vaccine administered. The frequency of TTS following a second dose of AstraZeneca Vaxzevria vaccine appears to be lower at about 1 per 520,000 doses administered. After the first dose, there was a higher reported incidence rate of TTS in the younger adults compared to the older adults. The reported incidence was also higher in women compared to men in some age groups. The case fatality rate ranges between 20 and 50%. Many cases have been reported to have serious long-term morbidity, including neurologic injury.

Anyone receiving a viral vector COVID-19 vaccine should be informed of the adverse event of TTS and advised to seek immediate medical attention if they develop symptoms following vaccination.

Symptoms of TTS may include:

Healthcare professionals should be aware of TTS including how to diagnose and treat the condition (see guidance from Thrombosis Canada).

Capillary leak syndrome (CLS) following vaccination with viral vector COVID-19 vaccines

Very rare cases of CLS have been reported following immunization with the viral vector COVID-19 vaccines (AstraZeneca Vaxzevria and Janssen Jcovden). CLS is a very rare, serious condition that causes fluid leakage from small blood vessels (capillaries), resulting in swelling mainly in the arms and legs, low blood pressure, thickening of the blood and low blood levels of albumin (an important blood protein). Symptoms are often associated with feeling faint (due to low blood pressure).

The frequency of CLS has been estimated at less than 1 per million doses of viral vector vaccines administered. Some of those affected had a history of CLS.

Immune thrombocytopenia (ITP) following vaccination with viral vector COVID-19 vaccines

Cases of immune thrombocytopenia with very low platelet levels (<20,000 per uL) have been reported very rarely after vaccination with Janssen Jcovden and AstraZeneca Vaxzevria COVID-19 vaccines, usually within the first four weeks after receiving Janssen Jcovden COVID-19 vaccine. This included cases with bleeding and cases with fatal outcome. Some of these cases occurred in individuals with a history of immune thrombocytopenia (ITP). If an individual has a history of ITP, the risks of developing low platelet levels should be considered before vaccination, and platelet monitoring is recommended after vaccination.

Guidance on reporting adverse events following immunization (AEFI)

Vaccine providers are asked to report AEFIs through local public health departments and to follow AEFI reporting requirements that are specific to their province or territory. In general, any serious (defined as resulting in hospitalization, permanent disability or death) or unexpected adverse event that is temporally related to vaccination should be reported. Refer to Reporting AEFI in Canada for additional information on the completion and submission of AEFI reports.

At the international level, the Brighton Collaboration has developed a list of Adverse Events of Special Interest (AESI). AESI are pre-specified medically significant events that have the potential to be causally associated with a vaccine product. Refer to Brighton Collaboration: COVID-19 resources and tools for the list of AESIs and for case definitions of specific AEFIs.

Refer to Adverse Events Following Immunization (AEFI) in Part 2 for additional information on definitions, reporting, investigating and managing, and causality assessments for AEFIs.

Refer to the PHAC weekly report for reported adverse events following COVID-19 vaccination in Canada.

Contraindications and precautions

Contraindications

Thrombosis with thrombocytopenia syndrome (TTS) following vaccination

Patients who have experienced venous and/or arterial thrombosis with thrombocytopenia following vaccination with a viral vector COVID-19 vaccine should not receive a subsequent dose of a viral vector COVID-19 vaccine. They may receive further doses of mRNA COVID-19 vaccines following consultation with their clinical team which may include a hematologist.

Capillary leak syndrome (CLS)

As a precautionary measure following the international cases that have been reported, individuals with a history of CLS (related or not to previous vaccination) should not receive viral vector COVID-19 vaccines.

Precautions

Hypersensitivity and allergies

Severe immediate allergic reaction (e.g., anaphylaxis) to a COVID-19 vaccine or a vaccine excipient

In individuals with a history of a severe, immediate (≤4h following vaccination) allergic reaction (e.g., anaphylaxis) after previous administration of an mRNA COVID-19 vaccine, re-vaccination may be offered with the same vaccine or the same mRNA platform if a risk assessment deems that the benefits outweigh the potential risks for the individual and if informed consent is provided. Consultation with an allergist or other appropriate physician should be sought prior to re-vaccination. If re-vaccinated, vaccine administration should be done in a controlled setting with expertise and equipment to manage anaphylaxis. Individuals should be observed for at least 30 minutes after re-vaccination. For example, a longer period of observation is warranted for individuals exhibiting any symptom suggestive of an evolving AEFI at the end of the 30-minute observation period.

For those with a previous history of allergy to an mRNA vaccine where consultation with an allergist or other appropriate physician precludes further vaccination with an mRNA vaccine, re-vaccination with Novavax Nuvaxovid or Medicago Covifenz may be preferred for individuals in the authorized age group without contraindications to the vaccine.

In individuals with a history of a severe, immediate (≤4h following vaccination) allergic reaction (e.g., anaphylaxis) after previous administration of a viral vector COVID-19 vaccine, re-vaccination may be offered with an mRNA platform if a risk assessment deems that the benefits outweigh the potential risks for the individual and if informed consent is provided. If re-vaccinated, individuals should be observed for an extended period of at least 30 minutes after re-vaccination.

Confirmed allergies to a component of a COVID-19 vaccine

Ingredients of authorized COVID-19 vaccines that have been associated with allergic reactions in other products are: polyethylene glycol [PEG] (included in the Pfizer-BioNTech Comirnaty original, Pfizer-BioNTech Comirnaty Bivalent, Moderna Spikevax original, Moderna Spikevax Bivalent and a trace amount in the Medicago Covifenz vaccines), tromethamine [trometamol or Tris] (included in the Pfizer-BioNTech Comirnaty Bivalent, Moderna Spikevax original, Moderna Spikevax Bivalent, as well as the pediatric 10 mcg and the grey cap, no dilution 30 mcg formulations of the Pfizer-BioNTech Comirnaty original vaccine) and polysorbate 80 (included in the Medicago Covifenz, Novavax Nuvaxovid, AstraZeneca Vaxzevria and Janssen Jcovden COVID-19 vaccines). There is a potential of cross-reactive hypersensitivity between PEG and polysorbate. There are also trace amounts of kanamycin and carbenicillin in the Medicago Covifenz vaccine.

In individuals with a confirmed severe, immediate (≤4h following exposure) allergy (e.g., anaphylaxis) to a component of a specific COVID-19 vaccine or its container (e.g., PEG), consultation with an allergist is recommended before receiving the specific COVID-19 vaccine. In individuals with a serious PEG allergy in whom mRNA vaccination is precluded based on a consultation with an allergist or other appropriate physician: for these individuals in the authorized age group without contraindications to the vaccine, Novavax Nuvaxovid may be preferred.

Adolescents and adults who are allergic to tromethamine (found in the Moderna Spikevax original and the Moderna Spikevax Bivalent vaccines) should be offered the Pfizer-BioNTech Comirnaty original (30 mcg) vaccine (vials with purple cap and purple label boarder only) which does not contain this excipient. Individuals who are allergic to polysorbates (found in viral vector vaccines, Medicago Covifenz and Novavax Nuvaxovid), should be offered an mRNA vaccine.

It is important to note that other, less serious reactions may mimic allergic reactions (e.g., vasovagal syncope) and vaccination is not contraindicated in these cases.

Mild to moderate immediate allergic reactions to a COVID-19 vaccine or a vaccine excipient

In individuals with mild to moderate immediate allergic reactions (defined as limited in the scope of symptoms and involvement of organ systems or even localized to the site of administration) to a previous dose of mRNA COVID-19 vaccine or any of its components, re-vaccination may be offered with the same vaccine or the same platform (i.e., mRNA). Assessment by a physician or nurse with expertise in immunization may be warranted prior to re-immunization.

Most instances of anaphylaxis to a vaccine begin within 30 minutes after administration of the vaccine. Therefore, if re-vaccination is chosen, an extended period of observation post-vaccination of at least 30 minutes should be provided for the aforementioned individuals.

Other allergies

The following individuals may be routinely vaccinated with COVID-19 vaccines

30 minute post-vaccination observation period:

15 minute post-vaccination observation period:

Acute illness

Vaccination of individuals who may be currently infected with SARS-CoV-2 is not known to have a detrimental effect on the illness. However, vaccination should be deferred in symptomatic individuals with confirmed or suspected SARS-CoV-2 infection, or those with respiratory symptoms, to minimize the risk of COVID-19 transmission at an immunization clinic/venue. If any person is identified with symptoms on arrival at the venue, they should not be immunized and should be instructed to seek medical and public health advice and follow current local public health measures.

As a precautionary measure and in light of the need to be able to monitor for COVID-19 vaccine adverse events without potential confounding from symptoms of COVID-19 or other co-existing illnesses, people should wait until all symptoms of an acute illness are resolved before vaccinating with a COVID-19 vaccine.

Hematologic

In individuals with bleeding disorders, the condition should be managed prior to immunization to minimize the risk of bleeding. Individuals receiving long-term anticoagulation are not considered to be at higher risk of bleeding complications following immunization and may be safely immunized without discontinuation of their anticoagulation therapy.

Immune thrombocytopenia (ITP)

If an individual has a history of ITP, the risks of developing low platelet levels should be considered before vaccination with a viral vector vaccine, and platelet monitoring is recommended after vaccination.

Individuals should seek immediate medical attention if they develop symptoms such as unexplained bleeding, unexplained bruising, or small purplish spots beyond the site of vaccination.

Venous thromboembolism (VTE)

In individuals with a pre-existing increased risk for thromboembolism, the possible increased risk of VTE with vaccine use should be considered.

Individuals should seek immediate medical attention if they develop symptoms, such as shortness of breath, chest pain, leg pain, leg swelling, or persistent abdominal pain following vaccination.

Thrombosis with thrombocytopenia syndrome (TTS)

There is no evidence that individuals with previous cerebral venous sinus thrombosis (CVST) with thrombocytopenia not related to a viral vector or people with previous heparin-induced thrombocytopenia (HIT) not related to a viral vector vaccine are at increased risk of VITT compared to other individuals after receiving a viral vector vaccine. However, similar to other individuals, an mRNA vaccine is preferred. The Novavax Nuvaxovid or Medicago Covifenz may be used among individuals in the authorized age group without contraindications to the vaccine who are not able or willing to receive an mRNA vaccine.

Myocarditis and/or pericarditis following vaccination

As a precautionary measure until more information is available, further doses of mRNA COVID-19 vaccines should be deferred among individuals who have experienced myocarditis and/or pericarditis within 6 weeks following a previous dose of an mRNA COVID-19 vaccine in most circumstances. This includes any person who had an abnormal cardiac investigation including ECG, elevated troponins, echocardiogram or cardiac MRI after a dose of an mRNA COVID-19 vaccine.

Those with a history compatible with pericarditis and who either had no cardiac workup or had normal cardiac investigations, can receive the next dose once they are symptom-free and at least 90 days have elapsed since vaccination.

Some individuals 5 years of age and older with confirmed myocarditis and/or pericarditis after a dose of an mRNA COVID-19 vaccine may choose to receive another dose of vaccine after discussing the risk and benefit with their healthcare provider. If another dose of vaccine is offered, they should be offered Pfizer-BioNTech Comirnaty original COVID-19 vaccine (at the age-appropriate dose) due to the lower reported rate of myocarditis and/or pericarditis following the Pfizer-BioNTech Comirnaty original (30 mcg) vaccine compared to the Moderna Spikevax original (100 mcg) vaccine among individuals 12 years of age and older. Informed consent should include discussion about the unknown risk of recurrence of myocarditis and/or pericarditis following receipt of additional doses of Pfizer-BioNTech Comirnaty original vaccine in individuals with a history of confirmed myocarditis and/or pericarditis after a previous dose of mRNA COVID-19 vaccine, as well as the need to seek immediate medical assessment and care should symptoms develop.

There have been case reports of myocarditis and/or pericarditis following the administration of Novavax Nuvaxovid. Information currently available is insufficient to determine a causal relationship with the vaccine.

Individuals who have a history of myocarditis unrelated to mRNA COVID-19 vaccination should consult their clinical team for individual considerations and recommendations. If the diagnosis is remote and they are no longer followed clinically for cardiac issues, they should receive the vaccine.

Guillain-Barré syndrome

Individuals with past history of GBS unrelated to COVID-19 vaccination should receive an mRNA COVID-19 vaccine. When mRNA COVID-19 vaccines are contraindicated, individuals may receive a viral vector COVID-19 vaccine after weighing the risks and benefits in consultation with their health care provider.

Individuals who developed GBS after a previous dose of a COVID-19 vaccine may receive another dose of an mRNA COVID-19 vaccine, after consultation with their health care provider (i.e., if the benefits outweigh the risk and informed consent is provided).

Bell's palsy

Individuals should seek medical attention if they develop symptoms compatible with Bell's palsy following receipt of mRNA COVID-19 vaccines. Healthcare providers should consider Bell's palsy in their evaluation if the patient presents with clinically compatible symptoms after an mRNA COVID-19 vaccine. Investigations should exclude other potential causes of facial paralysis.

Multisystem inflammatory syndrome in children or adults (MIS-C or MIS-A)

For children or adults with a previous history of MIS-C or MIS-A, vaccination should be postponed until clinical recovery has been achieved or until it has been ≥ 90 days since diagnosis, whichever is longer.

Other considerations

Drug interactions

There have been no drug interactions studies performed to date.

For more information about potential interactions with products containing anti-SARS-CoV-2 antibodies, refer to Blood products, human immunoglobulin and timing of immunization.

Tuberculin skin testing (TST) or interferon gamma release assay (IGRA)

There is a theoretical risk that mRNA or viral vector vaccines could temporarily affect cell-mediated immunity, resulting in false-negative TST or IGRA test results. However, there is no direct evidence for this interaction. Therefore, in the absence of data and acknowledging the importance of both timely tuberculosis testing and immunization, vaccination with COVID-19 vaccines may take place at any time before, after or at the same visit as the TST or IGRA test. Repeat tuberculin skin testing or IGRA (at least 4 weeks post-COVID-19 immunization) of individuals with negative TST or IGRA results for whom there is high suspicion of latent tuberculosis infection may be considered in order to avoid missing persons with TB infection.

Blood products, human immunoglobulin and timing of immunization

It is recommended that COVID-19 vaccines should not be given concurrently with anti-SARS-CoV-2 monoclonal antibodies.  

Administration of these products concurrently may result in decreased effectiveness of the COVID-19 vaccine and/or anti-SARS-CoV-2 monoclonal antibodies. Anti-SARS-CoV-2 monoclonal antibodies have high affinity for the spike protein expressed by COVID-19 vaccines, which could prevent the production of antibodies stimulated by the vaccine, or binding of vaccine antigen to the monoclonal antibody may neutralize the antibody.

Pre-exposure prophylaxis for COVID-19 with anti-SARS-CoV-2 monoclonal antibodies

Evusheld (AstraZeneca) is currently the only anti-SARS-CoV-2 monoclonal antibody authorized in Canada for prophylaxis against COVID-19. Some clinicians may choose to immunize with both COVID-19 vaccine and Evusheld. Administration of Evusheld and COVID-19 vaccines should be assessed in consultation with clinical experts. Clinicians may consider the following factors when assessing the potential benefits or risks when recommending Evusheld to their patients: the degree of immunocompromise, the presence of additional risk factors for severe COVID-19, the likelihood of not responding to COVID-19 vaccine, the risk of exposure to COVID-19 due to occupational or residential circumstances, as well as local circulation of variants with the potential for resistance to Evusheld. Although Evusheld could reduce humoral immune responses to a COVID-19 vaccine, cellular immune responses may not be impacted by Evusheld. Cellular immune responses to a COVID-19 vaccine are important for immunocompromised populations and, to sustain cellular immune responses, vaccination should not be withheld from this group.

Implementation advice to inform decision-makers on the appropriate use of Evusheld (e.g., patient prioritization) is available from the Canadian Agency for Drugs and Technologies in Health (CADTH), the Institut national d'excellence en santé et en services sociaux (INESSS ) and Ontario Health.

Guidance on anti-SARS-CoV-2 monoclonal antibodies may change as additional evidence emerges.

Administration of Evusheld following COVID-19 vaccines

To minimize interference, it is recommended that Evusheld should be administered at least 2 weeks following COVID-19 vaccination.

Administration of COVID-19 vaccines following Evusheld

There is no evidence on which to base a specific minimum interval for COVID-19 vaccination following Evusheld administration, though it should be noted that both Evusheld dosage (300mg vs. 600mg) and time since administration are expected to influence potential interactions or interference with COVID-19 vaccines. Timing should be assessed in consultation with clinical experts on a case-by-case basis.

Therapeutic management of COVID-19 with anti-SARS-CoV-2 monoclonal antibodies

Multiple products are authorized in Canada for therapeutic management of COVID-19. Expert clinical opinion should be sought on a case-by-case basis when deciding whether anti-SARS-CoV-2 monoclonal antibodies would be appropriate to administer following receipt of COVID-19 vaccine, taking into consideration the significance of the exposure, the risk of severe COVID-19 disease in the individual, and whether or not the degree of immunocompromise is such that response to the vaccine is unlikely.

Timing of administration of COVID-19 vaccines following administration of therapeutic or post-exposure anti-SARS-CoV-2 monoclonal antibodies should be assessed in consultation with clinical experts on a case-by-case basis.

For complete prescribing information, consult the product leaflet or information contained within the product monograph available through Health Canada's Drug Product Database.

Chapter revision process

This chapter was updated to reflect guidance based on current evidence and the National Advisory Committee on Immunization’s (NACI’s) expert opinion since the last version of this chapter (August 29, 2022). Additional content changes may reflect changes to COVID-19 vaccine product monographs. Refer to the Table of Updates for additional information.

For supporting information on COVID-19 vaccine chapter updates, including additional references, refer to the Current and/or Previous summary of updates in the Canadian Immunization Guide published on the NACI webpage under COVID-19.

Acknowledgements

This chapter was prepared by SJ Ismail, K Young, MC Tunis, A Killikelly, R Stirling, O Baclic, J Zafack, MI Salvadori, N Forbes, L Coward, C Jensen, R Krishnan, NK Abraham, E Abrams, Y-E Chung, B Warshawsky, E Wong, K Farrah, J Montroy, R Pless, A Nam, C Quach, R Harrison, and S Deeks on behalf of NACI.

NACI gratefully acknowledges the contribution of: M Laplante, C Mauviel, K Ramotar, N St-Pierre, S Pierre, N Mohamed, E Tice.

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