Recommendation on the use of mRNA COVID-19 vaccines in adolescents 12 to 17 years of age

Publication date: August 27, 2021

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Preamble

The National Advisory Committee on Immunization (NACI) is an External Advisory Body that provides the Public Health Agency of Canada (PHAC) with independent, ongoing and timely medical, scientific, and public health advice in response to questions from PHAC relating to immunization.

In addition to burden of disease and vaccine characteristics, PHAC has expanded the mandate of NACI to include the systematic consideration of programmatic factors in developing evidence-based recommendations to facilitate timely decision-making for publicly funded vaccine programs at provincial and territorial levels.

The additional factors to be systematically considered by NACI include: economics, ethics, equity, feasibility, and acceptability. Not all NACI Statements will require in-depth analyses of all programmatic factors. While systematic consideration of programmatic factors will be conducted using evidence-informed tools to identify distinct issues that could impact decision-making for recommendation development, only distinct issues identified as being specific to the vaccine or vaccine-preventable disease will be included.

This statement contains NACI's independent advice and recommendations, which are based upon the best current available scientific knowledge. This document is being disseminated for information purposes. People administering the vaccine should also be aware of the contents of the relevant product monograph. Recommendations for use and other information set out herein may differ from that set out in the product monographs of the Canadian manufacturers of the vaccines. Manufacturer(s) have sought approval of the vaccines and provided evidence as to its safety and efficacy only when it is used in accordance with the product monographs. NACI members and liaison members conduct themselves within the context of PHAC's Policy on Conflict of Interest, including yearly declaration of potential conflict of interest.

Background

The Pfizer-BioNTech and Moderna COVID-19 vaccines are mRNA vaccines that were initially authorized by Health Canada for use in individuals 16 and 18 years of age and older, respectively, in December 2020. On May 5, 2021, Health Canada expanded the Interim Order authorization for the Pfizer-BioNTech COVID-19 vaccine to also include adolescents 12 to 15 years of age based on clinical trial results in this age group. On August 27, 2021, Health Canada expanded the Interim Order authorization for the Moderna COVID-19 vaccine to also include adolescents 12 to 17 years of age.

As per the Health Canada-approved product monograph, the Pfizer-BioNTech COVID-19 vaccine is to be administered via intramuscular (IM) injection, 2 doses, 30mcg mRNA per dose, 3 weeks apart, and the Moderna COVID-19 vaccine is to be administered via IM injection, 2 doses, 100mcg mRNA per dose, 4 weeks apart. Additional information on mRNA COVID-19 vaccines can be found here: Health Canada's Drug Product Database. The COVID-19 vaccine dosing intervals recommended by NACI for adults in Canada also apply to adolescents.

On May 18, 2021, following Health Canada authorization of the Pfizer-BioNTech COVID-19 vaccine for 12 to 15 years of age, NACI recommended the use of the vaccine in adolescents (Strong NACI Recommendation) based on a review of available evidence including additional clinical trial results in the adolescent population. Since then, NACI has reassessed its recommendations on the use of mRNA COVID-19 vaccines in adolescents, considering additional evidence including clinical data on the efficacy, safety, and immunogenicity of the Moderna COVID-19 vaccine in adolescents as well as post-market safety and effectiveness reports on both mRNA COVID-19 vaccines.

For further information, please refer to NACI's Recommendations on the use of COVID-19 vaccines.

Methods

On May 9, 2021, NACI reviewed the available evidence on the use of the Pfizer-BioNTech COVID-19 vaccine in adolescents 12 to 15 years of age (manufacturer's clinical data in the regulatory submission to Health Canada). On June 15, 2021, NACI reviewed the available evidence on the use of Moderna COVID-19 vaccine in adolescents 12 to 17 years of age (manufacturer's clinical data in the regulatory submission to Health Canada). Additionally, NACI reviewed evidence of post-market safety and effectiveness of mRNA vaccines on January 19 and 28; April 1; June 2, 9, 15, 21, and 24; July 8 and 27; and August 3, 2021. Ethical considerations related to COVID-19 vaccination in adolescents were discussed with the Public Health Ethics Consultative Group (PHECG) on May 3 and July 6, 2021. The Canadian Immunization Committee (CIC) as well as Provincial and Territorial Chief Medical Officers of Health provided feedback on key policy questions to ensure alignment with program needs on May 6, 2021 and June 11, 2021, respectively. NACI approved the updated recommendation on the use of mRNA COVID-19 vaccines in adolescents on August 9, 2021.

Details of NACI's evidence-informed recommendation development process can be found elsewhere Footnote 1Footnote 2.

Summary of evidence

COVID-19 burden of disease in adolescents

Since the beginning of the COVID-19 pandemic, the rate of COVID-19 in Canadian adolescents has been similar to that observed in young adults. 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. Adolescents 12 to 17 years of age account for approximately 8% of the population Footnote 3, and this age group constitutes approximately 7% of COVID-19 cases reported nationally Footnote 4. In contrast, adolescents 12 to 17 years of age account for approximately 0.6% of COVID-19 cases resulting in hospitalization, approximately 0.4% of COVID-19 cases admitted to ICU, and approximately 0.01% of cases resulting in death (January 1, 2020 to August 13, 2021) Footnote 4. Since May 2021 (coinciding with both the increasing prominence of the B.1.617.2 Delta variant and decreasing number of adult hospitalization events), the relative burden of disease for adolescents 12 to 17 years of age shifted upwards to approximately 8% of COVID-19 cases, 1.2% of COVID-19 cases resulting in hospitalization, 0.8% of COVID-19 cases admitted to ICU and 0.08% of cases resulting in death Footnote 4. These estimates are limited to the case reports provided by the provinces and territories and therefore do not account for all cases that have occurred in Canada Footnote 5. As of August 13, 2021, over 70% of adolescents 12 to 17 years of age had received at least one dose of an mRNA COVID-19 vaccine [at the time when only the Pfizer-BioNTech vaccine was authorized] and more than 50% had received both doses Footnote 6.

Adolescents are at risk of multisystem inflammatory syndrome in children (MIS-C) following infection with SARS-CoV-2. This is a serious, though uncommon, condition associated with COVID-19 in children and adolescents Footnote 7. The mechanisms of MIS-C are not well understood but include a dysregulated immune response to SARS-CoV-2 infection Footnote 8. A 2020 study from the United States (US) found that MIS-C incidence was highest in children 5 years of age or less and between 6 to 10 years of age, with adjusted incidence estimated at 4.9 (95% CI: 3.7 to 6.6) and 6.3 (95% CI: 4.8 to 8.3) per 1,000,000 person-months, respectively. Incidence was lower for older children and adolescents aged 11 to 15 and 16 to 20 years old, with estimated adjusted incidence of 3.8 (95% CI: 2.8 to 5.3) and 2.4 (95% CI: 1.6 to 3.5) per 1,000,000 person-months respectively Footnote 9. As of August 12, 2021, 135 laboratory-confirmed and/or epidemiologically linked cases of MIS-C were reported in Canada, with a median age of six years Footnote 4. However, this count is likely an underestimate; 250 cases were reported that fulfilled WHO criteria for MIS-C but did not meet the criteria for laboratory-confirmed or probable SARS-CoV-2 infection. Of the 135 lab-confirmed cases, 27 cases occurred in adolescents 12 to 18 years old Footnote 4. Emerging evidence available in preprint suggests approximately 1 out of 3 cases of MIS-C reported in Canada were admitted to ICU for treatment Footnote 10.

Adolescents are also at risk of indirect consequences of the COVID-19 pandemic. For example, national survey data Footnote 11 and cross-sectional studies Footnote 12Footnote 13 suggest that children and adolescents in Canada have experienced deteriorations in mental health during the pandemic. Similar trends have been identified in other countries, with studies on mental health impacts reporting higher rates in adolescents of depression, anxiety, and stress, compared to before the pandemic Footnote 14Footnote 15. Significant increases in adolescent inpatient admissions for eating disorders have also been observed in Canada Footnote 16 and internationally Footnote 17. School closures and social isolation from other public health measures have had disproportionate impacts on marginalized youth, such as racialized and Indigenous groups, persons with disabilities, refugees and other newcomers to Canada, persons living in low-income settings, and persons of diverse sexual orientations and gender identities Footnote 15Footnote 18Footnote 20.

The studies referenced above were identified by a non-systematic search of evidence, and therefore caution should be taken in the interpretation of the findings.

Risk factors most frequently associated with severe disease in adolescents

There is emerging evidence on risk factors for severe COVID-19 disease in adolescents and children. An updated rapid review of risk factors for severe COVID-19 conducted by the Alberta Research Centre for Health Evidence (ARCHE) was completed in May 2021 Footnote 21. The review found a moderate certainty of evidence of ≥2-fold increase in COVID-19 associated hospitalizations in individuals 21 years of age and younger with 2 or more chronic conditions (versus no chronic conditions).

Several North American studies have highlighted the proportion of hospitalized pediatric/adolescent COVID-19 cases with underlying conditions and commonly reported underlying conditions. In a national prospective study led by the Canadian Paediatric Surveillance Program, a total of 264 children hospitalized with documented SARS-CoV-2 infection were reported between April 8 and December 31, 2020, through weekly surveys to a network of over 2,800 paediatricians Footnote 22. At least one underlying comorbidity was reported in 39.3% of children admitted because of COVID-19, with the most common comorbidities reported as obesity, asthma, epilepsy, chronic encephalopathy with severe neurodisability, chronic lung disease, and neurodevelopmental disorders. In unadjusted analyses, hospitalized children with obesity, chronic neurological conditions, or non-asthma chronic lung diseases were associated with greater diseases severity Footnote 22. A US cross-sectional study of 43,465 patients with COVID-19 aged 18 years and younger reported over 25% had one or more underlying condition, with the most common conditions reported including asthma, obesity, neurodevelopmental disorders, and certain mental health conditions Footnote 23. Another US-based report based on surveillance data of 204 adolescents aged 12 to 17 years who were hospitalized for probable/confirmed COVID-19 from January 1 to March 31, 2021 found that approximately 70% had one or more underlying medical conditions, where the most common conditions reported were obesity, chronic lung disease (including asthma), and neurologic disorders Footnote 24.

Evolving evidence of indirect protection from COVID-19 vaccines in non-vaccinated populations

There has been increasing evidence of significant indirect protection of unimmunized individuals living in households (25-29) and communities Footnote 30 in which the majority of the population has been vaccinated with either one or two doses of an mRNA COVID-19 vaccine. The likelihood of household transmission among unvaccinated residents of households in which at least one member of the household was vaccinated has been reported to be reduced by up to 90% Footnote 28. However, despite increasing vaccine coverage in adults, outbreaks in adolescents and children are occurring, including with the more transmissible Delta variant (31-33).

Direct protection of mRNA vaccines against SARS-CoV-2 Delta variant

Throughout June, the Delta variant was responsible for an increased proportion of confirmed COVID-19 cases and has now surpassed the Alpha variant as the most prevalent variant of concern (VOC) in circulation in Canada and internationally Footnote 34. Emerging evidence suggests that while the Delta variant is more transmissible than previous VOCs Footnote 35, a complete 2-dose vaccination series with an mRNA COVID-19 vaccine remains effective against symptomatic infection as well as COVID-19 associated hospitalization, ICU admission, and death Footnote 36Footnote 37. However, breakthrough infections with the Delta variant are being reported at higher frequency than with the Alpha variant Footnote 36Footnote 37.

Emerging real-world evidence reported in preprints noted somewhat higher effectiveness data against the Delta variant for one dose of the Moderna COVID-19 vaccine compared to one dose of the Pfizer-BioNTech COVID-19 vaccine Footnote 38Footnote 39, which is consistent with reports of higher immunogenicity for Moderna compared to Pfizer-BioNTech Footnote 40.

Clinical trial data on mRNA COVID-19 vaccines in adolescent populations

The Pfizer-BioNTech COVID-19 vaccine was evaluated in 2,260 adolescent participants 12 to 15 years of age as an amendment to study C4591001, an ongoing randomized, observer-blind, placebo-controlled Phase 3 trial Footnote 41. Participants were randomized to receive either two doses of the vaccine (30mcg mRNA each dose) (n=1,131) or placebo (n=1,129), 21 days apart. All adolescent study participants were recruited from the United States between October 15, 2020 and January 21, 2021. Almost half (49.0%) of adolescent participants were female and the median age of adolescent participants at vaccination was 14.0 years (range: 12 to 15 years). After the second dose, 98.3% of all adolescent participants had ≥ 1 month of follow-up while 57.9% had ≥ 2 months of follow-up at time of reporting. Follow up will continue in trial participants for at least 2 years following the second dose for ongoing safety reporting to Health Canada.

The Moderna COVID-19 vaccine was evaluated in 3,732 adolescent participants aged 12 to 17 years as part of an ongoing, Phase 2/3, randomized, observer-blind, placebo-controlled study Footnote 42. Participants were recruited between December 9, 2020 and February 28, 2021, and were randomized 2:1 to receive either two doses of the vaccine (100mcg mRNA each dose) (n=2,489) or a placebo (n=1,243), 28 days apart. All adolescent study participants were recruited from the US. Almost half (48.6%) of adolescent participants were female, 2,767 (74.3%) were aged 12 to 15 years, and 959 (25.7%) were aged 16 to 17 years. After the second dose, 97.3% of all participants had ≥ 1 month of follow-up while 41.9% had ≥ 2 months of follow-up.

Efficacy

In adolescent study participants 12 to 15 years of age without prior evidence of SARS-CoV-2 infection, the estimate of vaccine efficacy of the Pfizer-BioNTech COVID-19 vaccine against the first occurrence of confirmed symptomatic COVID-19 disease from 7 days after dose 2 was 100% (95% CI: 75.3 to 100.0%; 16 cases in the placebo group, 0 cases in the vaccine group). The estimate of vaccine efficacy in all participants 12 to 15 years of age (including those with prior evidence of SARS-CoV-2 infection) was also 100% (95% CI: 78.1 to 100.0%; 18 cases in the placebo group, and 0 cases in the vaccine group).

After dose one, there were 3 cases of confirmed COVID-19 identified in the Pfizer-BioNTech vaccine group and 35 cases identified in the placebo. All cases in the vaccine group occurred less than 11 days after dose 1, before a response to the vaccine would be expected (no cases were observed between 14 days after dose 1 and the time that dose 2 was administered).

For the Moderna COVID-19 vaccine (where the clinical trial had twice as many participants in the vaccine group than the placebo group), the estimate of efficacy against confirmed symptomatic COVID-19 disease starting 14 days after dose 2 in study participants 12 to 17 years of age without prior evidence of SARS-CoV-2 infection was 100% (95% CI: 29.0% to not evaluable; 4 cases in the placebo group, 0 cases in the vaccine group). The point estimate of efficacy against asymptomatic infection only (SARS-CoV-2 infection confirmed by either RT-PCR or serology) was 39.2%, starting 14 days after two doses of the vaccine, but the confidence interval around the point estimate was wide and included zero (95% CI: -24.7 to 69.7%; 16 cases out of 1,243 participants in the placebo group, 21 cases out of 2,489 participants in the vaccine group). The estimate of vaccine efficacy against asymptomatic infection should be interpreted with caution as cases identified due to a positive serology result are based on samples collected on Day 57 (i.e., 28 days after dose 2); therefore, this finding could reflect infection acquired at any time after dose 1 prior to the time of sample collection.

No estimate is available for the Moderna COVID-19 vaccine efficacy from 14 days after dose 1 until dose 2 was administered.

There were no cases of severe COVID-19, including deaths, reported in any of the adolescent study participants who received an mRNA vaccine (Pfizer-BioNTech or Moderna) or a placebo.

Immunogenicity

The humoral immune response following the second dose of a complete two-dose vaccination schedule with mRNA COVID-19 vaccines (Pfizer-BioNTech and Moderna) was non-inferior in adolescents compared to young adults, exceeding the 1.5-fold pre-established non-inferiority criterion for both studies (lower bound of the 2-sided 95% CI for the geometric mean ratio [GMR] >0.67). For Pfizer-BioNTech, SARS-CoV-2 50% neutralizing titers (NT-50) were assayed one month following dose 2, and the estimated ratio of antibody levels in adolescents (12 to 15 years of age; n=209) relative to young adults (16 to 25 years of age; n=186) was 1.76 (95% CI: 1.47 to 2.10). For Moderna, SARS-CoV-2 neutralizing titers (ID50) were assayed 28 days following dose 2, and the estimated ratio of antibody levels in adolescents (12 to 17 years of age; n=340) relative to young adults (18 to 25 years of age; n=305) was 1.077 (95% CI: 0.94 to 1.24). However, since no correlate of protection has been determined for COVID-19 at this time, it is unknown how the immune response levels that have been reported in clinical trials are related to prevention of SARS-CoV-2 infection or disease or the ability to transmit to others. Immunogenicity in adolescents following dose 1 was not reported in clinical trials for either Pfizer-BioNTech or Moderna COVID-19 vaccines

Safety

Consistent with clinical trial findings in individuals 16 to 25 years of age Footnote 43, the Pfizer-BioNTech COVID-19 vaccine was well tolerated in adolescents 12 to 15 years of age. Local reactions were mostly mild to moderate in severity and occurred more frequently following the first dose. The median onset of solicited local reactions was within the first 2 days after any dose and reactions persisted for a median of 1-3 days. Systemic events were predominantly fatigue, headaches, chills, muscle pain, fever, and joint pain (in order of descending frequency) and occurred more frequently after the second dose. The median onset day for most solicited systemic events after either dose of vaccine was 1 to 3 days post-vaccination, with a median duration of 1 day, except for fatigue and chills, which had median durations of 1 to 2 days. Compared to individuals 18 to 55 years of age, adolescents 12 to 15 years of age demonstrated increased frequency of headache, chills, and fever. Following the second dose, up to 64.5% of adolescent participants had headaches, up to 41.5% had chills, and up to 19.6% had fever Footnote 44. Vaccination-related lymphadenopathy in adolescents occurred in 0.6% of vaccine recipients (non-solicited adverse event), and no serious adverse events related to the vaccine, no cases of MIS-C, and no deaths were reported adolescents in the trial.

The Moderna COVID-19 vaccine was well tolerated in adolescents 12 to 17 years of age. Local reactions were mostly mild to moderate in severity and occurred similarly following the first and second doses. The majority of solicited local adverse reactions occurred within the first 1-2 days after each dose and persisted for a median of 3 days. In the vaccine group, axillary swelling or tenderness (a solicited adverse event) occurred in 23.3% of adolescents after dose 1 and 21.0% after dose 2. Systemic events were predominantly fatigue, headaches, muscle pain, chills, joint pain, nausea/vomiting, and fever (in order of descending frequency), and occurred more frequently after the second dose. The majority of solicited systemic adverse reactions occurred within the first 1-2 days after each dose and persisted for a median of 2 days. Solicited adverse reactions were generally similar between participants aged 12 to 15 years and participants aged 16 to 17 years and there were also no notable differences in the rates of reported unsolicited events between these age groups. Overall, in the vaccine groups, local reactogenicity was higher in adolescents compared with that observed in the adult Phase 3 study. In adolescents, there were no serious adverse events related to the vaccine, no cases of MIS-C, and no deaths reported in the trial.

Post-market safety data on myocarditis and pericarditis following vaccination with mRNA COVID-19 vaccines

Rare cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining around the heart) following vaccination with COVID-19 mRNA vaccines have been reported in Canada and internationally, including from Israel Footnote 33, the United States Footnote 45, Australia Footnote 46 and Europe Footnote 47. Symptoms of myocarditis/pericarditis can include shortness of breath, chest pain, or the feeling of a rapid or abnormal heart rhythm. Symptoms can be accompanied by abnormal test results (e.g., electrocardiogram, serum troponins, echocardiogram).

International cases are consistently reported to have occurred:

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

As of August 6, 2021, active and passive surveillance data from Canadian Adverse Events Following Immunization Surveillance System (CAEFISS) in combination with Canada Vigilance Database (CVD) indicates a higher number of myocarditis and/or pericarditis cases in younger age groups than would normally be expected Note de bas de page 48. Preliminary analyses suggest a higher unadjusted rate of myocarditis/pericarditis cases reported after vaccination with Moderna compared to Pfizer-BioNTech, however the analysis is ongoing.

Passive vaccine safety surveillance data alone from Ontario suggests a product-specific difference in the risk of myocarditis/pericarditis following mRNA vaccines, in particular following the second dose Note de bas de page 49. NACI reviewed an analysis restricted to medically reviewed AEFIs meeting levels 1-3 of the Brighton Collaboration case definitions Note de bas de page 50 for myocarditis and pericarditis with data as of July 26, 2021, and the data were subsequently updated through to August 7th, 2021 (n=204, data as of August 7, 2021) and published Note de bas de page 49. The dose 2 reporting rates for all ages/genders combined were 28.2 and 8.7 per million doses administered for the Moderna vaccine and the Pfizer-BioNTech vaccine, respectively. Product-specific trends continued to be observed when the analysis was restricted only to those events where the vaccine series was initiated on or after June 1, 2021 (n=54) to account for the enhanced surveillance of myocarditis/pericarditis cases and the expanded Moderna vaccine supply that began in June. In this restricted analysis from June 1, 2021, the product-specific rate of myocarditis/pericarditis following the second dose was higher for Moderna than Pfizer-BioNTech among 18-24 year old males (198.6 per million doses of the Moderna vaccine compared to 35.5 per million doses of the Pfizer-BioNTech vaccine). Additional analyses are ongoing. Please see Public Health Ontario Enhanced Epidemiological Summary on Myocarditis and Pericarditis Following Vaccination with COVID-19 mRNA Vaccines in Ontario: December 13, 2020 to August 7, 2021, for detailed analysis.

Similarly, higher rates of cases of myocarditis and/or pericarditis have been reported after the Moderna vaccine compared to Pfizer-BioNTech in the US, although verification of this potential difference is ongoing Footnote 45. An analysis of the US Vaccine Safety Datalink (VSD) data among individuals aged 12-39 years showed relatively higher frequencies observed after receipt of Moderna compared to Pfizer-BioNTech, however the reported rates were not statistically significantly different. Among individuals aged 12 to 39, VSD data showed more than double the rate of chart confirmed myocarditis and/or pericarditis following the second dose of the Moderna vaccine compared to the Pfizer-BioNTech vaccine (8 per 1,000,000 doses [95% CI: 3.2 to 16.5] vs. 19.8 per 1,000,000 doses [95% CI: 9.9 to 35.5]) Footnote 45.

Investigations into possible mechanisms of action that could explain the association between myocarditis and/or pericarditis and mRNA vaccines, identification of risk factors, including past history of myocarditis, and the potential impact of the interval between vaccine doses all continue in Canada and abroad Footnote 45Footnote 47Footnote 51Note de bas de page 52.

There are many potential causes for myocarditis and pericarditis, including both infectious and non-infectious causes, and disease severity can be variable. Myocarditis can also occur as a complication in people who are infected with SARS-CoV-2. A recent retrospective study from the US found myocarditis rates after confirmed COVID-19 infection to be as high as 450 cases per million infections in young males, aged 12-17 Footnote 53.

As part of ongoing COVID-19 vaccine safety efforts, the Public Health Agency of Canada (PHAC) and Health Canada are closely monitoring myocarditis and pericarditis through passive and active Canadian safety surveillance systems and collaboration with Canadian provincial and territorial health authorities, manufacturers and international regulators. Refer to the PHAC weekly AEFI report Footnote 48 for information on numbers of cases reported in Canada. Refer to Reporting Adverse Events Following Immunization (AEFI) in Canada Footnote 54 and to the recently developed Brighton Collaboration case definition of myocarditis/pericarditis Footnote 50 for additional information on the completion and submission of AEFI reports.

For further information, please refer to NACI's Recommendations on the use of COVID-19 vaccines; Vaccine safety and adverse events following immunization (AEFI).

Dose and route of administration

The dose and route of administration of the Pfizer-BioNTech and Moderna COVID-19 vaccines for adolescents (12 years of age and older) are identical to the respective dose and route in adults. For further information, please refer to NACI's Recommendations on the use of COVID-19 vaccines; Vaccine administration.

Recommendations

NACI recommends 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. (Strong NACI Recommendation)

Informed consent for all mRNA COVID-19 vaccines should include the following information:

Additional considerations, summary of evidence, and rationale

Research priorities

References

Footnote 1

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Footnote 3

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Footnote 5

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Footnote 7

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Footnote 8

Feldstein LR, Tenforde MW, Friedman KG, Newhams M, Rose EB, Dapul H, et al. Characteristics and outcomes of US children and adolescents with multisystem inflammatory syndrome in children (MIS-C) compared with severe acute COVID-19. JAMA. 2021 Mar 16;325(11):1074,1087. doi: 10.1001/jama.2021.2091.

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Footnote 9

Payne AB, Gilani Z, Godfred-Cato S, Belay ED, Feldstein LR, Patel MM, et al. Incidence of multisystem inflammatory syndrome in children among US persons infected with SARS-CoV-2. JAMA Netw Open. 2021 Jun 1;4(6):e2116420. doi: 10.1001/jamanetworkopen.2021.16420.

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Footnote 10

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Footnote 11

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Footnote 12

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Footnote 13

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Footnote 14

Racine N, McArthur BA, Cooke JE, Eirich R, Zhu J, Madigan S. Global prevalence of depressive and anxiety symptoms in children and adolescents during COVID-19: A meta-analysis. JAMA Pediatr. 2021 Aug 9:e212482. doi: 10.1001/jamapediatrics.2021.2482.

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Footnote 15

Jones EAK, Mitra AK, Bhuiyan AR. Impact of COVID-19 on mental health in adolescents: A systematic review. Int J Environ Res Public Health. 2021 Mar 3;18(5):2470. doi: 10.3390/ijerph18052470.

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Footnote 16

Spettigue W, Obeid N, Erbach M, Feder S, Finner N, Harrison ME, et al. The impact of COVID-19 on adolescents with eating disorders: a cohort study. J Eat Disord. 2021 Jun 4;9(1):65. doi: 10.1186/s40337-021-00419-3.

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Footnote 17

Schwartz MD, Costello KL. Eating disorder in teens during the COVID-19 pandemic. J Adolesc Health. 2021 May;68(5):1022. doi: 10.1016/j.jadohealth.2021.02.014.

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Footnote 18

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Footnote 19

Mental Health Commission of Canada. Lockdown life: Mental health impacts of COVID-19 on youth in Canada [Internet]. Ottawa (ON): Mental Health Commission of Canada; 2020 [cited 2021 Jun 22]. Available from: https://www.mentalhealthcommission.ca/sites/default/files/2021-02/lockdown_life_eng.pdf.

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Footnote 20

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Footnote 21

Gates M, Pillay J, Wingert A, Guitard S, Rahman S, Zakher B, et al. Risk factors associated with severe outcomes of COVID-19: An updated rapid review to inform national guidance on vaccine prioritization in Canada. medRxiv. 2021 May 22. doi: 10.1101/2021.04.23.21256014v2.

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Footnote 22

Drouin O, Moore-Hepburn C, Farrar DS, Baerg K, Chan K, Cyr C, et al. Characteristics of children hospitalized with acute SARS-CoV-2 infection in Canada. CMAJ. 2021. Forthcoming.

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Footnote 23

Kompaniyets L, Agathis NT, Nelson JM, Preston LE, Ko JY, Belay B, et al. Underlying medical conditions associated with severe COVID-19 illness among children. JAMA Netw Open. 2021 Jun 1;4(6):e2111182. doi: 10.1001/jamanetworkopen.2021.11182.

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Footnote 24

Havers FP, Whitaker M, Self JL, Chai SJ, Kirley PD, Alden NB, et al. Hospitalization of adolescents aged 12-17 years with laboratory-confirmed COVID-19 - COVID-NET, 14 States, March 1, 2020-April 24, 2021. MMWR Morb Mortal Wkly Rep. 2021 Jun 11;70(23):851,857. doi: 10.15585/mmwr.mm7023e1.

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Footnote 25

Harris RJ, Hall JA, Zaidi A, Andrews NJ, Dunbar JK, Dabrera G, et al. Impact of vaccination on household transmission of SARS-COV-2 in England [Internet]. [Preprint]. 2021 Apr 28. Available from: https://khub.net/documents/135939561/390853656/Impact+of+vaccination+on+household+transmission+of+SARS-COV-2+in+England.pdf/35bf4bb1-6ade-d3eb-a39e-9c9b25a8122a?t=1619601878136.

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Footnote 26

Salo J, Hägg M, Kortelainen M, Leino T, Saxell T, Siikanen M, et al. The indirect effect of mRNA-based Covid-19 vaccination on unvaccinated household members. medRxiv. 2021 May 29. doi: 10.1101/2021.05.27.21257896.

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Footnote 27

Shah ASV, Gribben C, Bishop J, Hanlon P, Caldwell D, Wood R, et al. Effect of vaccination on transmission of COVID-19: an observational study in healthcare workers and their households. medRxiv. 2021 Mar 21. doi: 10.1101/2021.03.11.21253275.

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Footnote 28

Prunas O, Warren JL, Crawford FW, Gazit S, Patalon T, Weinberger DM, et al. Vaccination with BNT162b2 reduces transmission of SARS-CoV-2 to household contacts in Israel. medRxiv. 2021 Jul 16. doi: 10.1101/2021.07.13.21260393.

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Footnote 29

Layan M, Gilboa M, Gonen T, Goldenfeld M, Meltzer L, Andronico A, et al. Impact of BNT162b2 vaccination and isolation on SARS-CoV-2 transmission in Israeli households: an observational study. medRxiv. 2021 Jul 16. doi: 10.1101/2021.07.12.21260377.

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Footnote 30

Milman O, Yelin I, Aharony N, Katz R, Herzel E, Ben-Tov A, et al. Community-level evidence for SARS-CoV-2 vaccine protection of unvaccinated individuals. Nat Med. 2021 Jun 10. doi: 10.1038/s41591-021-01407-5.

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Footnote 31

Riley S, Wang H, Eales O, Haw D, Walters CE, Ainslie KEC, et al. REACT-1 round 12 report: resurgence of SARS-CoV-2 infections in England associated with increased frequency of the Delta variant. medRxiv. 2021 Jun 21. doi.org/10.1101/2021.06.17.21259103.

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Footnote 32

Ontario COVID-19 Science Advisory Table. Ontario dashboard: The race against delta [Internet]. Toronto (ON); 2021 [cited 2021 Jul 13]. Available from: https://covid19-sciencetable.ca/ontario-dashboard/.

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Footnote 33

Gov.il. Surveillance of myocarditis (inflammation of the heart muscle) cases between December 2020 and May 2021 (including). Press release [Internet]. Israel: Ministry of Health; 2021 Jun 6 [cited 2021 Jun 22]. Available from: https://www.gov.il/en/departments/news/01062021-03.

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Footnote 34

GISAID. Tracking of variants [Internet]. Munich: Freunde von GISAID e.V.; 2021 Aug 16 [cited 2021 Aug 17]. Available from: https://www.gisaid.org/hcov19-variants/.

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Footnote 35

Campbell F, Archer B, Laurenson-Schafer H, Jinnai Y, Konings F, Batra N, et al. Increased transmissibility and global spread of SARS-CoV-2 variants of concern as at June 2021. Euro Surveill. 2021 Jun;26(24):2100509. doi: 10.2807/1560-7917.ES.2021.26.24.2100509.

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Footnote 36

Iorio A, Little J, Linkins L, Abdelkader W, Bennett D, Lavis JN. COVID-19 living evidence profile #6 (version 6.15): What is the efficacy and effectiveness of available COVID-19 vaccines in general and specifically for variants of concern? [Internet]. Hamilton (ON): Health Information Research Unit; 2021 Aug 11 [cited 2021 Aug 17]. Available from: https://www.mcmasterforum.org/docs/default-source/product-documents/living-evidence-syntheses/covid-19-living-evidence-synthesis-6.15---what-is-the-efficacy-and-effectiveness-of-available-covid-19-vaccines-in-general-and-specifically-for-variants-of-concern.pdf.

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Footnote 37

Public Health Agency of Canada (PHAC) Emerging Science Group (ESG). Living summary of SARS-CoV-2 variants of concern: The Delta variant (B.1.617.2) profile, Highlights up to July 29, 2021. Ottawa (ON): PHAC; 2021 Jul.

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Footnote 38

Nasreen S, Chung H, He S, Brown KA, Gubbay JB, Buchan SA, et al. Effectiveness of COVID-19 vaccines against variants of concern in Ontario, Canada. medRxiv. 2021 Jul 16. doi: 10.1101/2021.06.28.21259420.

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Footnote 39

Puranik A, Lenehan PJ, Silvert E, Niesen MJM, Corchado-Garcia J, O'Horo JC, et al. Comparison of two highly-effective mRNA vaccines for COVID-19 during periods of Alpha and Delta variant prevalence. medRxiv. 2021 Aug 9. doi: 10.1101/2021.08.06.21261707:2021.08.06.21261707.

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Footnote 40

McDonald I, Murray SM, Reynolds CJ, Altmann DM, Boyton RJ. Comparative systematic review and meta-analysis of reactogenicity, immunogenicity and efficacy of vaccines against SARS-CoV-2. NPJ Vaccines. 2021 May 13;6(1):74. doi: 10.1038/s41541-021-00336-1.

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Footnote 41

Frenck RW, Klein NP, Kitchin N, Gurtman A, Absalon J, Lockhart S, et al. Safety, immunogenicity, and efficacy of the BNT162b2 Covid-19 Vaccine in adolescents. N Engl J Med. 2021 May 27. doi: 10.1056/NEJMoa2107456.

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Footnote 42

Ali K, Berman G, Zhou H, Deng W, Faughnan V, Coronado-Voges M, et al. Evaluation of mRNA-1273 SARS-CoV-2 vaccine in adolescents. N Engl J Med. 2021 Aug 11. doi: 10.1056/NEJMoa2109522.

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Footnote 43

Ali K, Berman G, Zhou H, Deng W, Faughnan V, Coronado-Voges M, et al. Evaluation of mRNA-1273 SARS-CoV-2 vaccine in adolescents. N Engl J Med. 2021 Aug 11. doi: 10.1056/NEJMoa2109522.

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Footnote 44

Pfizer Canada. Product Monograph. Pfizer-BioNTech COVID-19 Vaccine. COVID-19 mRNA Vaccine, suspension for intramuscular injection [Internet]. Ottawa (ON): Health Canada; 2021 May 5 [cited 2021 May 13]. Available from: https://covid-vaccine.canada.ca/info/pdf/pfizer-biontech-covid-19-vaccine-pm1-en.pdf.

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Footnote 45

Shimabukuro, T. COVID-19 Vaccine safety updates [slides presented at Advisory Committee on Immunization Practices (ACIP) meeting] [Internet]. Atlanta (GA): Centers for Disease Control and Prevention (CDC); 2021 Jun 23 [cited 2021 Jun 25]. Available from: https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2021-06/03-COVID-Shimabukuro-508.pdf.

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Footnote 46

Therapeutic Goods Administration (TGA). COVID-19 vaccine weekly safety report [Internet]. Canberra: Department of Health, Australian Government; 2021 Aug 5 [cited 2021 Aug 18]. Available from: https://www.tga.gov.au/periodic/covid-19-vaccine-weekly-safety-report-05-08-2021.

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Footnote 47

European Medicines Agency (EMA). COVID-19 vaccines: update on ongoing evaluation of myocarditis and pericarditis [Internet]. Amsterdam: EMA; 2021 Jun 11 [cited 2021 Jun 14]. Available from: https://www.ema.europa.eu/en/news/covid-19-vaccines-update-ongoing-evaluation-myocarditis-pericarditis.

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Footnote 48

Public Health Agency of Canada (PHAC). Reported side effects following COVID-19 vaccination in Canada [Internet]. Ottawa (ON): Government of Canada; 2021 Aug 13 [cited 2021 Aug 18]. Available from: https://health-infobase.canada.ca/covid-19/vaccine-safety/.

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Footnote 49

Ontario Agency for Health Protection and Promotion (Public Health Ontario). Myocarditis and pericarditis following vaccination with COVID-19 mRNA vaccines in Ontario: December 13, 2020 to August 7, 2021 [Internet]. Toronto (ON): Queen's Printer for Ontario; 2021 [cited 2021 Aug 25]. Available from: https://www.publichealthontario.ca/-/media/documents/ncov/epi/covid-19-myocarditis-pericarditis-vaccines-epi.pdf?sc_lang=en

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Footnote 50

Brighton Collaboration. Myocarditis/pericarditis case definition [Internet]. Decatur (GA): The Task Force for Global Health; 2021 Jul 16 [cited 2021 Aug 18]. Available from: https://brightoncollaboration.us/myocarditis-case-definition-update/.

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Footnote 51

Bozkurt B, Kamat I, Hotez PJ. Myocarditis with COVID-19 mRNA vaccines. Circulation. 2021 Aug 10;144(6):471,484. doi: 10.1161/CIRCULATIONAHA.121.056135.

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Footnote 52

Luk A, Clarke B, Dahdah N, Ducharme A, Krahn A, McCrindle B, et al. Myocarditis and pericarditis following COVID-19 mRNA vaccination: Practical considerations for care providers. Can J Cardiol. 2021 Aug 7:S0828-282X(21)00624-3. doi: 10.1016/j.cjca.2021.08.001.

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Footnote 53

Singer ME, Taub IB, Kaelber DC. Risk of myocarditis from COVID-19 infection in people under age 20: A population-based analysis. medRxiv. 2021 Jul 27. doi: 10.1101/2021.07.23.21260998.

Return to footnote 53 referrer

Footnote 54

Public Health Agency of Canada (PHAC). Reporting Adverse Events Following Immunization (AEFI) in Canada: User guide to completion and submission of the AEFI reports [Internet]. Ottawa (ON): Government of Canada; 2019 [cited 2021 Aug 18]. Available from: https://www.canada.ca/en/public-health/services/immunization/reporting-adverse-events-following-immunization/user-guide-completion-submission-aefi-reports.html.

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Acknowledgments

This statement was prepared by: N Forbes, K Farrah, B Warshawsky, O Baclic, R Stirling, J Zafack, R Krishnan, J Montroy, M Salvadori, K Young, M Tunis, R Harrison and S Deeks on behalf of NACI.

NACI gratefully acknowledges the contribution of: K Ramotar, N St-Pierre, L Coward, A Jirovec, E Wong, SH Lim, N Alluqmani, S Ismail, and the NACI Secretariat.

NACI Members: S Deeks (Chair), R Harrison (Vice-Chair), J Bettinger, N Brousseau, P De Wals, E Dubé, V Dubey, K Hildebrand, K Klein, J Papenburg, C Rotstein, B Sander, S Smith, and S Wilson.

Former member: C Quach (Chair)

Liaison representatives: LM Bucci (Canadian Public Health Association), E Castillo (Society of Obstetricians and Gynaecologists of Canada), A Cohn (Centers for Disease Control and Prevention, United States), L Dupuis (Canadian Nurses Association), J Emili (College of Family Physicians of Canada), D Fell (Canadian Association for Immunization Research and Evaluation), M Lavoie (Council of Chief Medical Officers of Health), D Moore (Canadian Paediatric Society), M Naus (Canadian Immunization Committee), A Pham-Huy (Association of Medical Microbiology and Infectious Disease Canada), P Emberley (Canadian Pharmacists Association), L Bill (Canadian Indigenous Nurses Association), and S Funnel (Indigenous Physicians Association of Canada).

Ex-officio representatives: V Beswick-Escanlar (National Defence and the Canadian Armed Forces),, E Henry (Centre for Immunization and Respiratory Infectious Diseases [CIRID], PHAC), M Lacroix (Public Health Ethics Consultative Group, PHAC), C Lourenco (Biologic and Radiopharmaceutical Drugs Directorate, Health Canada), S Ogunnaike-Cooke (CIRID, PHAC), K Robinson (Marketed Health Products Directorate, HC), G Poliquin (National Microbiology Laboratory, PHAC), and T Wong (First Nations and Inuit Health Branch, Indigenous Services Canada).

NACI High Consequence Infectious Disease Working Group

Members: S Deeks (Chair), R Harrison (Vice-Chair), Y-G Bui, K Dooling, K Hildebrand, M Miller, M Murti, J Papenburg, R Pless, S Ramanathan, N Stall, and S Vaughan.

PHAC Participants: N Abraham, YE Chung, L Coward, N Forbes, C. Jensen, A Killikelly, R Krishnan, J Montroy, A Nam, M Patel, M Salvadori, A Sinilaite, R Stirling, E Tice, B Warshawsky, R Ximenes MW Yeung, and J Zafack.

Abbreviations

Abbreviation Term

AEFI
Adverse event following immunization
ARCHE
Alberta Research Center for Health Evidence
CI
Confidence Interval
CIC
Canadian Immunization Committee
COVID-19
Coronavirus disease 2019
EMA
European Medicines Agency
GMR
Geometric mean ratio
ICU
Intensive Care Unit
IM
Intramuscular
MCG
microgram
MIS-C
Multisystem Inflammatory Syndrome in Children
mRNA
Messenger Ribonucleic Acid
NACI
National Advisory Committee on Immunization
PHAC
Public Health Agency of Canada
PHECG
Public Health Ethics Consultative Group
RT-PCR
Reverse Transcription Polymerase Chain Reaction
SARS-CoV-2
Severe Acute Respiratory Syndrome Coronavirus 2
US
United States
VOC
Variant of Concern
VSD
Vaccine Safety Datalink (United States)
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