COVID-19 vaccine: Canadian Immunization Guide

Last partial content update (see Table of updates): January 2022

This chapter was updated based on the following statements from the National Advisory Committee on Immunization (NACI):

The COVID-19 vaccine recommendations section for "Individuals previously infected with SARS-CoV-2" has been updated and additional information provided in the rationale and evidence.

Additionally, the "Vaccine safety and adverse events" and "Precautions" sections were updated to reflect:

  • Updates to the product monographs of Pfizer Cominarty and Moderna Spikevax COVID-19 vaccines regarding Bell's palsy.
  • Updates to the product monographs of Janssen and AstraZeneca Vaxzevria COVID-19 vaccines regarding immune thrombocytopenia (ITP) and venous thromboembolism (VTE).

On this page

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 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.

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 and other immunocompromising conditions.

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 with COVID-19 have mild or no symptoms, some do become ill and require hospitalization. Adolescents generally present with mild illness and report few severe outcomes of COVID-19 (i.e., COVID-19 associated hospitalizations, ICU admission, and deaths) compared to older age groups.

Children and adolescents with SARS-CoV-2 infection are at risk of multisystem inflammatory syndrome in children (MIS-C), a rare but serious syndrome 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 the World Health Organization (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

mRNA vaccines

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.

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/COVISHIELD vaccine uses a modified chimpanzee adenovirus vector (ChAd) and the Janssen 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.

All authorized COVID-19 vaccines

When referring to COVID-19 vaccines throughout this chapter, only COVID-19 vaccines 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.

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

Refer to Table 1 in Contents of Immunizing Agents Authorized for Use in Canada in Part 1 for a list of all vaccines available for use in Canada and their contents.

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 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

The mRNA COVID-19 vaccines have been shown to be highly efficacious (approximately 91 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) adolescents (12 to 15), 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 mRNA vaccines are efficacious in individuals aged 12 years and over with or without evidence of prior SARS-CoV-2 infection (although the number of trial participants who had confirmed symptomatic COVID-19 was small). A second dose improved efficacy. Efficacy estimates for the Pfizer-BioNTech Comirnaty (10 mcg) vaccine in children aged 5 to 11 in individuals with evidence of prior SARS-CoV-2 infection are not currently known.

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 COVID-19 vaccine demonstrates moderate efficacy (approximately 67%) against symptomatic confirmed moderate to severe/critical COVID-19 infection from 14 days and 28 days post-vaccination. 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 potentially occur more quickly with the viral vector vaccines than the mRNA vaccines. Studies of vaccine efficacy against symptomatic infection after vaccination with the primary series suggest that protection with Moderna Spikevax may be more durable than with Pfizer-BioNTech Comirnaty. 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.

Effectiveness against severe disease

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. 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. Effectiveness estimates for the Pfizer-BioNTech Comirnaty (10 mcg) vaccine in children 5 to 11 years of age are not currently known.

Efficacy and effectiveness against asymptomatic infection and transmission

The Moderna Spikevax COVID-19 vaccine trial showed lower viral shedding between doses 1 and 2 in the group that received the vaccine compared to the placebo group. The AstraZeneca Vaxzevria viral vector vaccine did not demonstrate efficacy against asymptomatic infection, although the number of asymptomatic infections was small. The Janssen COVID-19 vaccine had moderate protection against asymptomatic and undetected COVID-19 infection. Studies are ongoing for these vaccines.

Estimates of vaccine effectiveness for the Pfizer-BioNTech Comirnaty COVID-19 vaccine in adults against asymptomatic infection were moderate to high after the first dose and high after the second dose. Similar results were reported for mRNA COVID-19 vaccines in general (i.e., Moderna Spikevax and Pfizer-BioNTech Comirnaty). There are no results specific to other COVID-19 vaccines yet, but studies are ongoing.

Recommendations for use

Children

Recommendations

It is recommended that a complete series with the Pfizer-BioNTech COVID-19 vaccine (10 mcg) may be offered to children 5 to 11 years of age who do not have contraindications to the vaccine, with a dosing interval of at least 8 weeks between first and second dose.

Considerations

Children who receive the 10 mcg Pfizer-BioNTech COVID-19 vaccine 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 COVID-19 vaccine that is authorized for individuals aged 12 years and older to complete their primary series. If the second dose of 10 mcg is given, the dose should still be considered valid and the series complete.

Currently, the risk of myocarditis/pericarditis in children following immunization with the 10 mcg dose of the Pfizer-BioNTech vaccine is unknown. Safety surveillance data from individuals aged 12 and older does not suggest the risk of myocarditis/pericarditis following mRNA COVID-19 vaccination would be greater in children aged 5 to 11 years compared to older populations.

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.

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

Rationale

The Pfizer-BioNTech vaccine for children 5 to 11 years of age is authorized as a primary series of two 10 mcg doses given 21 days apart. In adults, emerging 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 also be associated with a reduced risk of myocarditis/pericarditis following a second dose of an mRNA COVID-19 vaccine.

Evidence

The Pfizer-BioNTech COVID-19 vaccine (10 mcg dose) met non-inferiority criteria for generating a humoral immune response to the vaccine in children aged 5 to 11 years compared to young adults and adolescents aged 16 to 25 years (who received a 30 mcg dose). Interim phase 2/3 findings in children 5-11 years of age suggest the vaccine is efficacious at preventing symptomatic COVID-19, with a similar estimate of vaccine efficacy against symptomatic COVID-19 to that observed in individuals aged 12 years and over. The systemic reactogenicity profile in children ages 5 to 11 years (10 mcg dose) was lower than that observed for adolescents and young adults (who received a 30 mcg dose).

Adolescents

Recommendations

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.

Moderately to severely immunocompromised adolescents

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 Vaccination of specific populations including pregnancy and breastfeeding, individuals previously infected with SARS-CoV-2, persons with an autoimmune condition, immunocompromised persons, travellers, and persons new to Canada for additional considerations, rationale and evidence for vaccination of these populations.

Considerations

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.

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

Rationale

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 vaccine is preferred to the Moderna Spikevax vaccine in individuals 12 to 17 years of age because of a lower reported rate of myocarditis/pericarditis following the Pfizer-BioNTech (30 mcg) compared to the Moderna Spikevax (100 mcg) vaccine. Additionally, a longer interval between doses is associated with higher vaccine effectiveness and potentially lower risk of myocarditis/pericarditis.

Evidence

Evidence from pivotal clinical trials of the Pfizer-BioNTech Comirnaty COVID-19 vaccine in adolescents 12 to15 years of age, and the Moderna Spikevax COVID-19 vaccine in adolescents 12 to 17 years of age have demonstrated safety, immunogenicity and efficacy profiles similar to that previously reported in older individuals.

Post-market safety surveillance of mRNA COVID-19 vaccines has found an increased frequency of myocarditis and pericarditis most frequently in adolescents and younger adults aged 12 to 30 years of age, more frequently in males compared to females, and more frequently after the second dose. However, the majority of cases, while hospitalized, have been relatively mild and resolved quickly with conservative therapy and rest. Analyses of Canadian and international data (e.g., United States, France, Denmark, Finland, Norway, Sweden) show that with the primary series the incidence of myocarditis is rare with either mRNA vaccine, but higher following the Moderna 100 mcg vaccine compared to the Pfizer-BioNTech 30 mcg vaccine.

Adults

Recommendations

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

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:

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

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

Moderately to severely immunocompromised adults

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.

It is recommended that the additional dose for those who are moderately to severely immunocompromised be a viral vector vaccine only when other authorized COVID-19 vaccines are contraindicated or inaccessible.

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

Refer to Vaccination of specific populations including pregnancy and breastfeeding, individuals previously infected with SARS-CoV-2, persons with an autoimmune condition, immunocompromised persons, travellers, and persons new to Canada for additional considerations, rationale and evidence for vaccination of these populations.

Considerations

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.

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

Moderately to severely immunocompromised adults

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 100 mcg induces somewhat higher antibody levels compared to Pfizer BioNTech Comirnaty 30 mcg and protection (against infection and severe disease) from a primary series with Moderna Spikevax 100 mcg may be more durable than Pfizer-BioNTech Comirnaty 30 mcg.

In addition to the considerations listed above, informed consent should include discussion about the limited evidence on the use of viral vector COVID-19 vaccines in this population, and the lack of evidence on the use of an additional dose of viral vector COVID-19 vaccines in this population.

Rationale

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 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.

An 8-week interval between the first and second dose of mRNA vaccine should be provided as a longer interval between doses is associated with higher vaccine effectiveness and potentially lower risk of myocarditis/pericarditis.

Among adults aged 18 to 29 years, the use of the Pfizer-BioNTech vaccine is preferred to the Moderna vaccine because of a lower reported rate of myocarditis/pericarditis following the Pfizer-BioNTech (30 mcg) compared to the Moderna (100 mcg) vaccine at the mRNA primary vaccine series.

Among adults aged 30 years or older, either mRNA vaccine should be used to start or continue the mRNA vaccine series given that this age group has a lower risk of vaccine-associated myocarditis/pericarditis.

Schedule

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 COVID-19 vaccine should be offered a minimum of 28 days after AstraZeneca COVID-19 vaccine).

Recommendations on optimal intervals apply to all vaccine schedules. An interval longer than 28 days between doses is likely to result in a better immune response. However, some individuals (including moderately to severely immunocompromised individuals after a 1- or 2- dose 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.

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.

Table 1. Immunization schedule for a primary series, by COVID-19 vaccine
Vaccine product Immunization scheduleFootnote a Minimum interval Authorized interval Optimal intervalFootnote b
Pfizer-BioNTech Comirnaty (30mcg) 2-dose schedule 19 daysFootnote c 21 days 8 weeksFootnote d
Pfizer-BioNTech Comirnaty (10mcg, pediatric formulation) 2-dose schedule 19 days 21 days At least 8 weeksFootnote d
Moderna Spikevax (100 mcg) 2-dose schedule 21 daysFootnote e 28 days 8 weeksFootnote d
AstraZeneca Vaxzevria 2-dose scheduleFootnote f 28 days 4 to 12 weeks At least 8 weeks
Janssen COVID-19 vaccine 1-dose scheduleFootnote f N/A N/A N/A
Footnote a

Moderately to severely immunocompromised individuals should be immunized with a primary series of 3 doses with an mRNA COVID-19 vaccine. Refer to Table 2 and 3 for additional information.

Return to footnote a referrer

Footnote b

There is emerging 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, an 8-week interval for mRNA vaccine is recommended.

Return to footnote b referrer

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 to footnote c referrer

Footnote d

Emerging Canadian safety surveillance data suggest an extended interval between the first and second dose may reduce the risk of myocarditis/pericarditis following the second dose of an mRNA COVID-19 vaccine (note this data is currently under preparation for publication).

Return to footnote d referrer

Footnote e

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

Return to footnote e referrer

Footnote f

AstraZeneca Vaxzevria and Janssen COVID-19 vaccine are not authorized for use in individuals less than 18 years of age.

Return to footnote f referrer

Moderately to severely immunocompromised individuals ages 12 and older

Table 2. Immunization schedule for a primary series for moderately to severely immunocompromised individuals, by COVID-19 vaccine
Vaccine product Immunization scheduleFootnote a Minimum interval between the initial 2-doses Minimum interval between 1- or 2-dose primary series and the additional doseFootnote b
Pfizer-BioNTech Comirnaty (30 mcg) 3-dose schedule 19 daysFootnote c 28 days
Moderna Spikevax (100 mcg) 3-dose schedule 21 daysFootnote d 28 days
AstraZeneca VaxzevriaFootnote e 2-dose scheduleFootnote f
+1 mRNA
28 days 28 days
Janssen COVID-19 vaccineFootnote e 1-dose scheduleFootnote f
+ 1-mRNA
N/A 28 days
Footnote a

It is recommended that for moderately to severely immunocompromised adolescents and adults, 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.

Return to footnote a referrer

Footnote b

The minimum interval between the 1- or 2- dose primary series and the additional dose is 28 days. An interval longer than the minimum 28 days between doses is likely to result in a better immune response. However, if a longer interval is being considered, then risk factors for exposure and risk of severe disease should also be taken into account.

Return to footnote b referrer

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 to footnote c referrer

Footnote d

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

Return to footnote d referrer

Footnote e

AstraZeneca Vaxzevria and Janssen COVID-19 vaccine are not authorized for use in individuals less than 18 years of age.

Return to footnote e referrer

Footnote f

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

Return to footnote f referrer

Table 3. Options for completing COVID-19 vaccine primary series for moderately to severely immunocompromised individuals 12 years of age and older
Moderately to severely immunocompromised individual presents with a history of: Options to complete the primary COVID-19 seriesFootnote a
0 doses of COVID-19 vaccine 3 doses of mRNA COVID-19 vaccine
1 dose of mRNA COVID-19 vaccine 2 doses of mRNA COVID-19 vaccine
2 doses of mRNA COVID-19 vaccine 1 dose of mRNA COVID-19 vaccine
1 dose of AstraZeneca VaxzevriaFootnote b COVID-19 vaccine 2 doses of mRNA COVID-19 vaccine
2 doses of AstraZeneca VaxzevriaFootnote b COVID-19 vaccine 1 dose of mRNA COVID-19 vaccine
1 dose of JanssenFootnote b COVID-19 vaccine 1 dose of mRNA COVID-19 vaccine
Footnote a

It is recommended that for moderately to severely immunocompromised adolescents and adults 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.

Return to footnote a referrer

Footnote b

AstraZeneca Vaxzevria and Janssen COVID-19 vaccine are not authorized for use in individuals less than 18 years of age.

Return to footnote b referrer

Booster doses

Booster doses should be prioritized in the groups discussed below with particular emphasis on frontline health care workers and those at highest risk of severe illness from COVID-19, including those in older age groups and those with high-risk medical conditions.

Recommendations

An mRNA vaccine (either the Moderna Spikevax or Pfizer-BioNTech Comirnaty vaccine) should be used as an additional dose (regardless of which COVID-19 vaccine was used in the primary series) in populations for whom a booster dose is recommended.

A booster dose of an authorized mRNA COVID-19 vaccine should be offered ≥6 months after completion of a primary COVID-19 vaccine series to adults in the following populations:

A booster dose of an authorized mRNA COVID-19 vaccine may be offered ≥6 months after completion of a primary COVID-19 vaccine series to adults 18 to 49 years of age with consideration of jurisdictional and individual risks.

Refer to Updated guidance on booster COVID-19 vaccine doses in Canada, Table 2 for additional information on jurisdictional and individual risks.

Individuals less than 18 years of age

The use of mRNA or viral vector COVID-19 vaccines for booster doses is not currently authorized among individuals less than 18 years of age.

Vaccine options for adults 18 to 29 years of age

For adults 18 to 29 years of age the use of Pfizer-BioNTech Comirnaty booster dose (30 mcg dose) may be preferred over the Moderna Spikevax booster dose (50 mcg dose).

Vaccine options for adults 30 years of age and older

For adults 30 years of age and older either Moderna Spikevax or Pfizer-BioNTech Comirnaty vaccines may be used as a booster dose (regardless of which COVID-19 vaccine was used in the primary series).

If offering Moderna Spikevax the following doses may be preferred:

If offering Pfizer-BioNTech Comirnaty the following dose may be considered:

Moderately to severely immunocompromised individuals 18 years of age and older

For moderately to severely immunocompromised adults, a 100 mcg dose of Moderna Spikevax may be preferred. This is based on clinical discretion.

Refer to Table 4 for a summary of booster doses recommendations.

Table 4. Booster dose recommendations
Age Booster recommendations Products and dose for booster
70 years and over Should be offered a booster Footnote a Moderna 100 mcgFootnote b or Pfizer-BioNTech 30 mcg
50 to 69 years Should be offered a booster Footnote a Moderna 50 mcg Footnote b Footnote c or Pfizer 30 mcg
30 to 49 years May be offered a booster Footnote a Moderna 50 mcg Footnote b Footnote c or Pfizer-BioNTech 30 mcg
18 to 29 years May be offered a booster Footnote a Pfizer-BioNTech 30 mcg Footnote b Footnote c may be preferred
12 to 17 years Booster not recommended Not applicable
5 to 11 years Booster not recommended Not applicable
Footnote a

The following groups should receive a booster:

  • Adults who are frontline healthcare workers (having direct close physical contact with patients) regardless of the interval between doses in their primary series
  • Adults ≥50 years of age
  • Adults living in long-term care homes for seniors or other congregate living settings that provide care for seniors
  • Recipients of a viral vector vaccine series completed with only viral vector vaccines (AstraZeneca/COVISHIELD or Janssen COVID-19 vaccine)
  • Adults in or from First Nations, Inuit and Métis communities

Return to footnote a referrer

Footnote b

If Moderna Spikevax is being used as a booster for those who are: ≥70 years of age; adults living in long-term care homes for seniors or other congregate living settings that provide care for seniors; or are moderately to severely immunocompromised, 100 mcg may be preferred given evidence that it may have a slightly higher vaccine effectiveness. For moderately to severely immunocompromised adults, this is based on clinical discretion.

Return to footnote b referrer

Footnote c

If Moderna Spikevax is being used as a booster for those living in long-term care homes for seniors or other congregate living settings that provide care for seniors, 100 mcg may be preferred.

Return to footnote c referrer

Considerations

Informed consent should include discussion about what is known and unknown about the risks and benefits of providing a booster dose.

Additionally, 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.

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

Adults 18 to 29 years of age

For the booster dose, the use of the Pfizer-BioNTech 30 mcg booster dose may be preferred to the Moderna 50 mcg booster dose among eligible individuals as a precaution due to the lower reported rate of myocarditis/pericarditis following the Pfizer-BioNTech 30mcg vaccine compared to the Moderna 100 mcg vaccine (safety data specific to the lower Moderna 50 mcg booster dose are limited). Evidence following the Moderna Spikevax (50 mcg) booster dose is limited.

Adults > 70 years of age, adults living in long-term care homes for seniors or other congregate living settings that provide care for seniors and moderately to severely immunocompromised individuals

After the recommended primary series, either Moderna Spikevax or Pfizer Comirnaty (30 mcg) may be considered as a booster dose. If Moderna Spikevax is being used as the booster product, a 100 mcg dose may be preferred. Moderna Spikevax 100 mcg induces somewhat higher antibody levels compared to Pfizer BioNTech Comirnaty 30 mcg and protection (against infection and severe disease) from a primary series with Moderna Spikevax 100 mcg may be more durable than Pfizer-BioNTech Comirnaty 30 mcg. Currently there are no data comparing the immune responses after a booster vaccination with Moderna Spikevax (100 mcg) and Pfizer-BioNTech Comirnaty (30 mcg) in these populations.

Moderately to severely immunocompromised individuals 18 years of age and older

In addition to the considerations directly above, 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. While data on a fourth dose 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.

It should be noted that Moderna Spikevax (100 mcg) is not currently authorized by Health Canada as a booster dose.

Rationale

The intent of a booster dose is to restore protection that may have decreased over time to a level that is no longer deemed sufficient in individuals who initially responded adequately to a complete primary vaccine series. Doses of COVID-19 vaccines after the primary series are being described as booster doses. However, over time, the nomenclature of this additional dose could evolve as the optimal number of doses in a primary series is better understood.

Evidence

Evidence suggests protection against infection decreases with time from receipt of the second dose of vaccine. Evidence also shows that shorter intervals between doses in a primary series may result in lower immune responses and more rapid waning of protection. Populations at high risk of severe illness from COVID-19 or high risk of exposure to the COVID-19 virus were prioritized for early COVID-19 vaccination. Many people in these populations completed their primary vaccine series earlier than the general population and with shorter intervals of 21 to 28 days between doses.

Studies suggest that a booster dose of an mRNA COVID-19 vaccine produces a very high immune response that is generally higher than the immune response after the primary series, has a favourable safety profile, and provides good short-term protection against infection.

People who received a complete vaccine series of a viral vector vaccine (AstraZeneca Vaxzevria, Janssen) have somewhat lower initial vaccine effectiveness and may become susceptible to infection sooner than people who received a primary series that included at least 1 dose of an mRNA vaccine.

Vaccination of specific populations

Pregnancy and breastfeeding

Recommendations

It is recommended that a complete vaccine series with an mRNA COVID-19 vaccine should be preferentially offered to individuals in the authorized age group who are pregnant or breastfeeding.

It is recommended that a viral vector COVID-19 vaccine may be offered to individuals in the authorized age group who are pregnant or breastfeeding when other COVID-19 vaccines are contraindicated or inaccessible.

Since the beginning of the COVID-19 pandemic, evidence has evolved to indicate that pregnancy is a risk factor for severe outcomes of COVID-19. Pregnant or breastfeeding adults are included as those recommended to receive a booster dose.

Considerations

No specific safety signals have been detected related to pregnancy. Those who are trying to become pregnant do not need to avoid pregnancy after vaccination with an mRNA vaccine.

No specific safety signals have been detected with mRNA vaccination during breastfeeding and individuals should continue to breastfeed after vaccination.

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. Informed consent should also include discussion about emerging evidence on the safety of mRNA COVID-19 vaccines in these populations.

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 5).

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

Table 5: 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 vaccine 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 COVID-19 vaccine There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to Janssen COVID-19 vaccine during pregnancy. Women who are vaccinated with Janssen COVID-19 vaccine during pregnancy are encouraged to enroll in the registry by visiting C-VIPER: COVID-19 Vaccines International Pregnancy Exposure Registry.

Rationale

Compared to non-pregnant persons, SARS-CoV-2 infection in pregnancy may increase the risk of complications requiring hospitalization and intensive care, as well as poorer pregnancy outcomes including premature birth, stillbirth, and caesarean delivery.

During pregnancy, an mRNA vaccine is preferred due to reassuring published data on the safety of these vaccines in pregnancy.

Evidence

Pregnant or breastfeeding individuals were excluded from the mRNA and viral vector COVID-19 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.

Emerging 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 at least for 6 weeks after maternal vaccination with mRNA vaccines.

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

Individuals previously infected with SARS-CoV-2

Recommendations

It is recommended that mRNA COVID-19 vaccine should be offered to individuals with previous laboratory-confirmed SARS-CoV-2 infection who are in the authorized age group without contraindications.

A complete primary series may be offered in light of uncertainties about protection provided by previous infection.

The booster dose recommendations also apply to individuals with previous laboratory-confirmed SARS-CoV-2 infection. Refer to Booster doses for information regarding booster doses for adults 18 years of age and older.

It is recommended that before vaccination, the individual should no longer be considered infectious, and symptoms of an acute illness should be completely resolved. These waiting times are intended to, respectively, 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.

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

Considerations

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

There are also no notable specific safety signals following the first or second dose in this population.

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.

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

Rationale

Currently, the rationale to offer COVID-19 vaccination to those who were previously infected is that protection is expected to be more robust and longer-lasting with vaccination compared to SARS-CoV-2 infection alone. It is very important for previously infected individuals to be vaccinated against COVID-19 to decrease the risk of re-infection. As the safety profile for a second dose in those previously infected is similar or less reactogenic than that of the first dose, and COVID-19 vaccines have been better studied as 2-dose regimens, a complete series may be offered.

Evidence

To date, COVID-19 vaccine efficacy based on clinical trials is uncertain for previously infected individuals. The majority of available evidence on immunogenicity, safety and effectiveness has been in adults with previous infection, with limited evidence at this time in children.

Of those who received two doses of COVID-19 vaccine, individuals with previous infection will produce antibody titres that are higher than those in individuals without previous infection. Although antibody levels in both groups decrease, they stay higher in those with previous infection and vaccination. Protection conferred by infection and two doses of COVID-19 vaccine has also been found to last longer than protection from past infection alone.

The optimal time from infection to first dose of vaccine is not known. However, a longer interval may result in a more robust and durable immune response.

If a delay in administering vaccination following infection is being considered, risk factors for exposure (including local epidemiology and circulation of VOCs) and risk of severe disease should also be taken into account.

Persons with an autoimmune condition

Recommendations

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

It is recommended that a viral vector COVID-19 vaccine may be offered to individuals in the authorized age group with an autoimmune condition when other COVID-19 vaccines are contraindicated or inaccessible.

Considerations

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.

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

Safety data in these populations following vaccination with a viral vector vaccine are not available.

Rationale

The evidence about autoimmune conditions as an independent risk factor for severe COVID-19 is evolving.

Evidence

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.

Refer to Immunization in Persons with Chronic Diseases in Part 3 for additional general information on autoimmune conditions.

Immunocompromised persons

Recommendations

It is recommended that a complete COVID-19 vaccine series with an mRNA COVID-19 vaccine should be preferentially offered to individuals aged 12 years and older who are immunosuppressed due to disease or treatment.

For those who are moderately to severely immunocompromised in the authorized age group who 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 in the authorized age group 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 a mRNA COVID-19 vaccine should be offered.

A viral vector COVID-19 vaccine may be offered to individuals in the authorized age group who are immunosuppressed due to disease or treatment when other COVID-19 vaccines are contraindicated or inaccessible. It is recommended that the additional dose for those who are moderately to severely immunocompromised be a viral vector vaccine only when other COVID-19 vaccines are contraindicated or inaccessible.

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

Considerations

The minimal interval between the 1- or 2- dose initial 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 a 1- or 2- dose 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 immunosuppressed includes individuals with the following conditions:

Refer to Immunization of Immunocompromised Persons, Immunosuppressive therapy in Part 3 for a suggested definition of high dose steroids.

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. Informed consent should include discussion about the limited evidence on the use of viral vector COVID-19 vaccines in this population, and the lack of evidence on the use of an additional dose of viral vector COVID-19 vaccines in this population.

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

Rationale

Immunocompromised individuals, including those receiving immunosuppressive therapy, are at increased risk for prolonged infection and serious complications from SARS-CoV-2 infection.

Evidence

Participants in the COVID-19 vaccine clinical trials only included individuals who were not immunosuppressed, such as those with stable infection with human immunodeficiency virus (HIV), and those not receiving immunosuppressive therapy during the trial.

Studies have shown that immunogenicity is substantially decreased in some immunocompromised adults when compared to healthy vaccine recipients. Observational studies 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.

Emerging 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. Moderna Spikevax COVID-19 vaccine may produce a greater immune response in this population. Investigations are ongoing.

Based on observational studies the frequency and severity of adverse events following vaccination 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 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.

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 vaccine (30mcg)

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

Dilute with 1.8 mL 0.9% Sodium Chloride Injection, USP prior to use.

Each dose is 0.3 mL after dilution, containing 30 mcg of SARS-CoV-2 spike protein mRNA.

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 vaccine (10mcg, pediatric formulation)

This formulation has an orange vial cap 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.

Moderna Spikevax COVID-19 vaccine

Each dose is 0.5 mL, containing 100 mcg of SARS-CoV-2 spike protein mRNA.

A booster dose for select populations is 0.25 mL, containing 50 mcg of SARS-CoV-2 spike protein mRNA.

Refer to Booster doses for additional information.

No dilution is required.

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 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.

AstraZeneca Vaxzevria COVID-19 vaccines

While either an AstraZeneca Vaxzevria COVID-19 vaccine or an mRNA COVID-19 vaccine product may be offered for the subsequent dose in a 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.

Emerging 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.

Simultaneous administration with other vaccines

COVID-19 vaccines for children 5 to 11 years old should not routinely be given simultaneously (i.e., same day) with other vaccines (live or non-live). In the absence of evidence, it would be prudent to wait for a period of at least 14 days before or after the administration of another vaccine before administrating a COVID-19 vaccine to prevent erroneous attribution of an AEFI to one particular vaccine or the other. This suggested minimum waiting period between vaccines is precautionary at this time. Simultaneous administration or a shortened interval between COVID-19 vaccines and other vaccines may be warranted on an individual basis in some circumstances at the clinical discretion of the healthcare provider.

For adults and adolescents, COVID-19 vaccines may be given simultaneously with (i.e., same day), or at any time before or after, non-COVID-19 vaccines (including live and non-live vaccines).

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.

It is currently not known if the reactogenicity of COVID-19 vaccines is increased with simultaneous administration of other vaccines. No specific safety concerns have been identified to date. Studies to assess the safety and immunogenicity of simultaneous administration of COVID-19 vaccines with other vaccines are ongoing.

Refer to Timing of Vaccine Administration in Part 1 for additional general information on simultaneous 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) 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 or Moderna Spikevax) 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

Pfizer-BioNTech Comirnaty COVID-19 vaccine (30 mcg, vials with purple caps)

Frozen vials prior to use

The Pfizer-BioNTech Comirnaty COVID-19 vaccine must be stored at ultra-low temperatures of -90°C to -60°C and protected from light, in the original packaging, until ready to use.

Refer to the re-icing guidelines (available at Pfizer-BioNTech COVID-19 Vaccine) for instructions regarding the use of the manufacturer's original thermal container for temporary storage.

Vials may also be stored at -25°C to -15°C for up to 2 weeks. Vials must be kept frozen and protected from light, in the original cartons, until ready to use. Vials stored at -25°C to -15°C for up to 2 weeks may be returned 1 time to the recommended storage condition of -90°C to -60°C. Total cumulative time the vials are stored at -25°C to -15°C should be tracked and should not exceed 2 weeks.

Thawed, unpunctured vials (prior to dilution)

The Pfizer-BioNTech Comirnaty COVID-19 vaccine may be thawed and stored at +2°C to +8°C for up to 1 month or at room temperature (up to +25°C) for no more than 2 hours. During storage, minimize exposure to room light, and avoid exposure to direct sunlight and ultraviolet light. Thawed vials can be handled in room light conditions.

Do not refreeze thawed vials.

Thawed, punctured vials (after dilution)

The Pfizer-BioNTech Comirnaty COVID-19 vaccine must be stored between +2°C to +25°C and used within 6 hours from the time of dilution. During storage, minimize exposure to room light, and avoid exposure to direct sunlight and ultraviolet light. After dilution, the vaccine vials can be handled in room light conditions.

Pfizer-BioNTech Comirnaty COVID-19 vaccine (10 mcg, pediatric formulation, vials with orange caps)

Frozen vials prior to use

Cartons may arrive frozen in ultra-cold conditions at -25°C to -15°C. Once received, frozen vials may be immediately transferred to the refrigerator (2°C to 8°C), thawed and stored for up to 10 weeks.

Frozen vials may be stored in an ultra-low temperature freezer at -90°C to -60°C. Do not store vials at -25°C to -15°C (-13°F to 5°F).

Unopened multidose vial

Cartons may also arrive at +2°C to+ 8°C. If vials are received at +2°C to +8°C, they should be stored at +2°C to +8°C.

Thawed, unpunctured vials (prior to dilution)

Vials may be stored at temperatures up to +25°C for a total of 12 hours prior to dilution. Thawed vials can be handled in room light conditions.

Do not refreeze thawed vials.

Thawed, punctured vials (after dilution)

After dilution the vials should be stored at +2°C to +25°C. Vials should be discarded 12 hours after dilution (i.e., the first puncture).

Moderna Spikevax COVID-19 vaccine

Frozen vials prior to use

The Moderna Spikevax COVID-19 vaccine should be stored at temperatures of -25°C to -15°C and protected from light in the original packaging.

Thawed, unpunctured vials

If not punctured, the Moderna Spikevax COVID-19 vaccine can be thawed and stored at +2°C to +8°C for up to 30 days, or at +8°C to +25°C for up to 24 hours.

Do not refreeze thawed vials.

Thawed, punctured vials

The Moderna Spikevax COVID-19 vaccine can be stored between +2°C to below +25°C but must be discarded after 24 hours from the time of first puncture.

AstraZeneca Vaxzevria COVID-19 vaccine

Unopened multidose vial

The AstraZeneca Vaxzevria vaccine can be stored between +2ºC to +8ºC and protected from light in the original packaging. Do not freeze.

Opened multidose vial

After first opening, chemical and physical in-use stability has been demonstrated from the time of vial puncture to administration for no more than 6 hours at room temperature (up to +30ºC) or 48 hours in a refrigerator (+2ºC to +8ºC).

After the first puncture, the vial can be re-refrigerated, but the cumulative storage time at room temperature must not exceed 6 hours, and the total cumulative storage time must not exceed 48 hours. After this time, the vial must be discarded.

Janssen COVID-19 vaccine

Unopened multidose vial

The Janssen COVID-19 vaccine can be stored between +2ºC to +8ºC for a single period of up to 6 months, not exceeding the original expiry date (EXP). The vials must be protected from light in the original packaging.

The vaccine can also be stored frozen at -25°C to -15°C.

Thawed, unpunctured vials

When stored frozen at -25°C to -15°C, a carton of 10 vials or an individual vial should be thawed overnight at 2°C to 8°C. At room temperature (maximally 25°C), a carton of 10 vials will take approximately 4 hours to thaw, and an individual vial will take approximately 1 hour to thaw.

Do not refreeze thawed vials.

Punctured multidose vial

After the first dose has been withdrawn, the vial/filled syringe can be held at 2°C to 8°C for up to 6 hours or at room temperature (maximally 25°C) for up to 3 hours, after the first puncturing of the vial. Discard if vaccine is not used within this time.

For more 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 post-licensure COVID-19 vaccine pharmacovigilance, which is ongoing.

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.

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 COVID-19 vaccines. Compared to adolescents and young adults, children aged 5 to 11 years of age had similar frequencies of pain at the injection site and higher frequencies of swelling and redness. Localized axillary swelling and tenderness (lymphadenopathy) was a solicited adverse event in the Moderna Spikevax COVID-19 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 COVID-19 vaccines. Relative to adolescents and young adults, systemic adverse events in children aged 5 to 11 years of age were comparable and less frequent for some events (such as fever, chills, headache, and fatigue).

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

The safety profile after a second dose is similar or less reactogenic than that of the first dose in individuals with previous infection. In observational and clinical studies, occurrence of solicited and unsolicited systemic adverse events in individuals with prior SARS-CoV-2 infection was slightly higher compared to the SARS-CoV-2 naïve population, primarily in younger adults. There is limited evidence that adverse events in individuals who had mild illness were comparable to the SARS-CoV-2 naïve population, but slightly increased among those who had severe infection. Overall, there was no observed increase in the frequency of more severe adverse events in this population.

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.

To date, the available data does not indicate that vaccination of SARS-CoV-2 naïve individuals with COVID-19 vaccines will elicit enhanced or altered disease upon subsequent infection by SARS-CoV-2 (e.g., vaccine-enhanced disease).

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

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 Vaccine-induced immune thrombotic thrombocytopenia (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 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).

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 surveillance data in Canada, US and European Nordic countries suggests a higher rate of myocarditis/pericarditis cases reported after vaccination with Moderna Spikevax compared to Pfizer-BioNTech Comirnaty vaccine especially among 12 to 29 year old males following a second dose of vaccine. Additional analyses are ongoing.

Classic myocarditis (unrelated to COVID-19 disease) is less common in younger children 5 to 11 years of age. It is unknown whether myocarditis/pericarditis will occur after the lower doses of mRNA present within pediatric COVID-19 vaccines for children 5 to 11 years of age.

While long-term follow-up is ongoing, available data indicate that the majority of individuals affected, while hospitalized, have responded well to conservative therapy and tend to recover quickly.

It is currently unknown whether myocarditis/pericarditis will occur after the lower doses (10 mcg) of mRNA present within pediatric COVID-19 vaccines for children 5 to 11 years of age. Post market safety surveillance is ongoing.

Healthcare providers should consider myocarditis and/or 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 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.

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). 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 and AstraZeneca Vaxzevria COVID-19 vaccines, usually within the first four weeks after receiving Janssen 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.

Venous thromboembolism (VTE)

Venous thromboembolism (VTE) has been observed rarely following vaccination with the Janssen 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 and Moderna Spikevax). Investigations have identified an increased risk of GBS following vaccination with the viral vector COVID-19 vaccines (AstraZeneca Vaxzevria and Janssen). 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. Only 2 cases have been described in the literature: 1 following Pfizer-BioNTech Comirnaty 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) been reported following vaccination with COVID-19 mRNA vaccines (Pfizer-BioNtech or Moderna) 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/A) following vaccination with an mRNA COVID-19 vaccine

Very rare cases of MIS-C/A (multisystem inflammatory syndrome; in children and in adults, respectively) have been reported following vaccination with COVID-19 mRNA vaccines in Canada and internationally among individuals aged 12 years and older. However, on October 29, 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/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) following vaccination with mRNA COVID-19 vaccines have been reported at an incidence estimated between 2 to 10 cases per million doses of vaccine administered. 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. Emerging 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.

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.

In addition to provincial or territorial reporting requirements, the Brighton Collaboration has developed a list of Adverse Events of Special Interest (AESI) that are of particular interest and should be reported. 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.

Capillary leak syndrome (CLS)

As a precautionary measure following the international cases that have been reported, individuals with a history of capillary leak syndrome (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

mRNA vaccines

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, re-vaccination with an mRNA vaccine is preferred over a viral vector vaccine due to the better effectiveness and immunogenicity of mRNA vaccines and the possible adverse effects specifically associated with viral vector vaccines.

Viral vector vaccines

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 vaccines and Moderna Spikevax COVID-19 vaccines), tromethamine [trometamol or Tris] (included in the Moderna Spikevax COVID-19 vaccine and the pediatric 10 mcg formulation of the Pfizer-BioNTech Comirnaty vaccine) and polysorbate 80 (included in the AstraZeneca Vaxzevria and Janssen COVID-19 vaccines).

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.

Adolescents and adults who are allergic to tromethamine (found in the Moderna Spikevax product) should be offered the Pfizer-BioNTech 30 mcg Comirnaty vaccine which does not contain this excipient. Individuals who are allergic to polysorbates (found in viral vector vaccines), 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). Offering an mRNA vaccine is preferred over a viral vector vaccine (see above). 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, and they should only receive a viral vector COVID-19 vaccine if an mRNA vaccine is contraindicated or inaccessible and following an appropriate risk assessment.

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 (with or without pericarditis) within the 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 with confirmed myocarditis (with or without 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 30 mcg due to the lower reported rate of myocarditis and/or pericarditis following the Pfizer-BioNTech 30mcg vaccine compared to the Moderna 100 mcg vaccine. Informed consent should include discussion about the unknown risk of recurrence of myocarditis and/or pericarditis following receipt of additional doses of Pfizer-BioNtech COVID-19 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.

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 or inaccessible, 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 (MIS-C)

For children with a previous history of MIS-C, 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 may temporarily affect cell-mediated immunity, resulting in false-negative TST or IGRA test results. If tuberculin skin testing or an IGRA test is required, it should be administered and read before immunization or delayed for at least 4 weeks after vaccination. Vaccination with COVID-19 vaccines may take place at any time after all steps of tuberculin skin testing have been completed.

In cases where an opportunity to perform the TST or IGRA test might be missed, the testing should not be delayed since these are theoretical considerations. However, re-testing (at least 4 weeks post immunization) of individuals with negative results for whom there is high suspicion of tuberculosis infection may be prudent in order to avoid missing cases due to potentially false-negative results.

Blood products, human immunoglobulin and timing of immunization

It is recommended that COVID-19 vaccines should not be given simultaneously with monoclonal antibodies or convalescent plasma.

To date, there is insufficient evidence on the receipt of both a COVID-19 vaccine and anti-SARS-CoV-2 monoclonal antibodies or convalescent plasma for treatment or prevention. Therefore, timing of administration and potential interference between these 2 products are currently unknown. Administration of these products close together may result in decreased effectiveness of a COVID-19 vaccine and/or anti-SARS-CoV-2 monoclonal antibodies because the monoclonal antibodies have high affinity for the spike protein expressed by the vaccines, which could prevent the production of antibodies stimulated by the vaccine.

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

In the post-exposure setting, 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 after receipt of COVID-19 vaccine, taking into consideration the risk of exposure and the risk of severe COVID-19 disease in the individual.

Chapter revision process

This chapter was updated to reflect guidance published by the National Advisory Committee on Immunization (NACI) since the first version of this chapter. Additional content changes reflect changes to COVID-19 vaccine product monographs. Refer to the Table of Updates for additional information.

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, R Pless, A Nam, C Quach, R Harrison, and S Deeks on behalf of the High Consequence Infectious Disease Working Group (HCID WG) and was approved by NACI.

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

Selected references

Abraham N, Spruin S, Rossi T, Fireman B, Zafack J, Blaser C, et al. Myocarditis and/or Pericarditis Risk After mRNA COVID-19 Vaccination: A Canadian Head to Head Comparison of BNT162b2 and mRNA-1273 Vaccines. JVAC-D-21-03106, Available at SSRN: https://ssrn.com/abstract=3988612

AstraZeneca Canada Inc. Product monograph - Vaxzevria™. November 15, 2021.

Brighton Collaboration. Interim case definition of Thrombosis with Thrombocytopenia Syndrome (TTS) [Internet]. Decatur (GA): The Task Force for Global Health; 2021 Apr 21 [cited 2021 May 18]. Available from: https://brightoncollaboration.us/wp-content/uploads/2021/05/TTS-Interim-Case-Definition-v10.16.3-May-23-2021.pdf

Janssen Inc. Product monograph - Janssen COVID-19 vaccine. November 23, 2021.

ModernaTX, Inc. Product monograph - SPIKEVAX™. September 16, 2021.

National Advisory Committee on Immunization. Interim guidance on booster COVID-19 vaccine doses in Canada. October 29, 2021. Accessed October 2021 from: https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/recommendations-use-covid-19-vaccines/statement-guidance-booster-doses.html

National Advisory Committee on Immunization. Recommendations on the use of COVID-19 vaccines. October 22, 2021. Accessed October 2021 from: https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/recommendations-use-covid-19-vaccines.html

National Advisory Committee on Immunization. NACI rapid response: Booster dose in long-term care residents and seniors living in other congregate settings. September 28, 2021. Accessed October 2021 from: https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/statement-september-28-2021-booster-dose-long-term-care-residents-seniors-living-other-congregate-settings.html

National Advisory Committee on Immunization. NACI rapid response: Additional dose of COVID-19 vaccine in immunocompromised individuals following 1- or 2- dose primary series. September 10, 2021. Accessed October 2021 from: https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/statement-september-10-2021-additional-dose-covid-19-vaccine-immunocompromised-following-1-2-dose-series.html

National Advisory Committee on Immunization. Recommendation on the use of mRNA COVID-19 vaccines in adolescents 12 to 17 years of age. August 27, 2021. Accessed October 2021 from: https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/recommendations-use-covid-19-vaccines/mrna-adolescents.html

Pfizer Canada ULC. Product monograph - COMINARTY™. November 19, 2021.

Verity Pharmaceuticals Inc. Product monograph - COVISHIELD. August 13, 2021.

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