Archived 25: NACI rapid response: Updated recommendation on the use of authorized COVID-19 vaccines in individuals aged 12 years and older in the context of myocarditis and pericarditis reported following mRNA COVID-19 vaccines [2021-12-03]

Published: December 3, 2021

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This is an archived version. Please refer to current COVID-19 vaccine pages:

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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.


Cases of myocarditis/pericarditis have rarely been reported following mRNA COVID-19 vaccines globally, including in Canada, and the National Advisory Committee on Immunization (NACI) has been closely monitoring this vaccine safety signal.

Post-market safety surveillance on mRNA COVID-19 vaccines identified that when myocarditis and/or pericarditis occurs, it occurs usually within a week following vaccination, most frequently in adolescents and young adults (12 to 29 years of age), more frequently in males compared to females, and more frequently after the second dose as compared to the first.


On November 16, 2021, NACI reviewed the recent evidence on myocarditis/pericarditis following COVID-19 vaccination including data from Canada, Israel, the United States (US), France, and Nordic countries (Denmark, Finland, Norway, Sweden). NACI discussed this recent evidence while considering data on the epidemiology of COVID-19 infection, safety, immunogenicity, efficacy/effectiveness of COVID-19 vaccines as well as ethics, equity, feasibility, and acceptability.

Following a comprehensive review, NACI updated and approved its recommendations on the use of the COVID-19 vaccines authorized for use among individuals aged 12 years and older in the context of myocarditis and pericarditis following vaccination on November 25, 2021. NACI continues to review the evidence on the use of COVID-19 vaccines. Recommendations on re-vaccination of individuals aged 12 years and older with a history of myocarditis/pericarditis following a previous dose of an mRNA COVID-19 vaccine is not covered in this document but will be addressed in future updates. Refer to the full NACI Recommendations on the use of COVID-19 vaccines among individuals aged 12 years and older, and other NACI statements including Recommendation on the use of the Pfizer-BioNTech COVID-19 vaccine (10mcg) in children 5 to 11 years of age.

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


The previous NACI recommendation continues to be maintained:

  1. NACI preferentially recommends that a complete series with an mRNA COVID-19 vaccine should be offered to individuals 12 years and older without contraindications to the vaccine. (Strong NACI Recommendation)

In addition, NACI now recommends that :

1a. For individuals aged 12 to 29 years receiving an mRNA COVID-19 vaccine primary series:

1b. For individuals aged 18 to 29 years who are eligible to receive a booster dose of vaccine*:

1c. For individuals aged 30 years or older receiving an mRNA COVID-19 vaccine primary series or booster dose:

*The use of mRNA booster doses is not currently authorized among individuals aged less than 18 years.

NACI will continue to review the evidence as it emerges and update the recommendations as needed.

Rationale and additional considerations

Summary of evidence


For additional details on myocarditis/pericarditis following COVID-19 vaccination among individuals aged 12 years and older, refer to statements from NACI:


This statement was prepared by: J Zafack, B Warshawsky, M Salvadori, E Abrams, R Krishnan, R Pless, M Tunis, K Young, S Ismail, S Ogunnaike-Cooke, R Harrison, and S Deeks on behalf of NACI.

NACI gratefully acknowledges the contribution of: K Farrah, K Ramotar, N St-Pierre, 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, A Pham-Huy, C Rotstein, B Sander, S Smith, and S Wilson.

Liaison representatives: L Bill (Canadian Indigenous Nurses Association), LM Bucci (Canadian Public Health Association), E Castillo (Society of Obstetricians and Gynaecologists of Canada), A Cohn (Centers for Disease Control and Prevention, US), L Dupuis (Canadian Nurses Association), D Fell (Canadian Association for Immunization Research and Evaluation), S Funnell (Indigenous Physicians Association of Canada), J Hu / N Ivers (College of Family Physicians of Canada), M Lavoie (Council of Chief Medical Officers of Health), D Moore (Canadian Paediatric Society), M Naus (Canadian Immunization Committee), and A Ung (Canadian Pharmacists Association).

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), D MacDonald (Vaccine Safety, PHAC), S Ogunnaike-Cooke (CIRID, PHAC), G Poliquin (National Microbiology Laboratory, PHAC), K Robinson (Marketed Health Products Directorate, HC), and T Wong (First Nations and Inuit Health Branch, Indigenous Services Canada).

NACI Vaccine Safety Working Group

Members: J Bettinger (Chair), N Brousseau, E Castillo, D Danoff, V Dubey, D Fell, K Hildebrand, G Lacuesta, A Pham-Huy, B Seifert, K Top, S Wilson.

PHAC Participants: N Abraham, N Dayneka, C Jensen, R Krishnan, R Pless, A Shaw, B Warshawsky and J Zafack.

Table 1

Table 1. Strength of NACI recommendations
Strength of NACI recommendation
based on factors not isolated to strength of evidence
(e.g., public health need)
Strong Discretionary


"should/should not be offered"

"may/may not be offered"


Known/anticipated advantages outweigh known/anticipated disadvantages ("should"),


Known/anticipated disadvantages outweigh known/anticipated advantages ("should not")

Known/anticipated advantages are closely balanced with known/anticipated disadvantages, or uncertainty in the evidence of advantages and disadvantages exists


A strong recommendation applies to most populations/individuals and should be followed unless a clear and compelling rationale for an alternative approach is present.

A discretionary recommendation may/may not be offered for some populations/individuals in some circumstances. Alternative approaches may be reasonable.


Abbreviation Term

Coronavirus disease 2019
Messenger Ribonucleic Acid
National Advisory Committee on Immunization
Public Health Agency of Canada
United States
Vaccine-induced immune thrombotic thrombocytopenia


Footnote 1

Ismail SJ, Langley JM, Harris TM, Warshawsky BF, Desai S, FarhangMehr M. Canada's National Advisory Committee on Immunization (NACI): Evidence-based decision-making on vaccines and immunization. Vaccine. 2010;28:A58,63. doi: 10.1016/j.vaccine.2010.02.035.

Return to footnote 1 referrer

Footnote 2

Ismail SJ, Hardy K, Tunis MC, Young K, Sicard N, Quach C. A framework for the systematic consideration of ethics, equity, feasibility, and acceptability in vaccine program recommendations. Vaccine. 2020 Aug 10;38(36):5861,5876. doi: 10.1016/j.vaccine.2020.05.051.

Return to footnote 2 referrer

Footnote 3

Pollack A, Kontorovich AR, Fuster V, Dec GW. Viral myocarditis--diagnosis, treatment options, and current controversies. Nat Rev Cardiol. 2015 Nov;12(11):670,680. doi: 10.1038/nrcardio.2015.108.

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Footnote 4

Barda N, Dagan N, Ben-Shlomo Y, Kepten E, Waxman J, Ohana R, et al. Safety of the BNT162b2 mRNA Covid-19 vaccine in a nationwide setting. N Engl J Med. 2021 Sep 16;385(12):1078,1090. doi: 10.1056/NEJMoa2110475.

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Footnote 5

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.

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Footnote 6

Public Health Agency of Canada. Reported side effects following COVID-19 vaccination in Canada [Internet]. Ottawa (ON): Government of Canada; 2021 Nov [cited 2021 Nov 5]. Available from:

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Footnote 7

Su J.R. Myopericarditis following COVID-19 vaccination: Updates from the Vaccine Adverse Event Reporting System (VAERS) [slides presented at Advisory Committee on Immunization Practices (ACIP) meeting on October 21, 2021] [Internet]. Atlanta (GA): Centers for Disease Control and Prevention (CDC); 2021 Oct [cited 2021 Nov 26]. Available from:

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Footnote 8

Klein N. Myocarditis analyses in the Vaccine Safety Datalink: Rapid cycle analyses and "head-to-head" product comparisons [slides presented at Advisory Committee on Immunization Practices (ACIP) meeting October 21, 2021] [Internet]. Atlanta (GA): Centers for Disease Control and Prevention (CDC); 2021 Oct [cited 2021 Nov 26]. Available from:

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Footnote 9

Oster, M. mRNA COVID-19 vaccine-associated myocarditis [slides presented at Advisory Committee on Immunization Practices (ACIP) meeting November 2, 2021] [Internet]. Atlanta (GA): Centers for Disease Control and Prevention (CDC); 2021 Nov [cited 2021 Nov 10]. Available from:

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Footnote 10

Myocardite et péricardite après la vaccination Covid-19 [Internet]. Saint-Denis (France): EPI-PHARE; 2021 Nov 8 [cited 2021 Nov 26]. Available from:

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Footnote 11

COVID-19 subcommittee of the WHO Global Advisory Committee on Vaccine Safety (GACVS): updated statement regarding myocarditis and pericarditis reported with COVID-19 mRNA vaccines [Internet]. Geneva: World Health Organization (WHO); 2021 Oct 27 [cited 2021 Nov 26]. Available from:

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Footnote 12

Polack FP, Thomas SJ, Kitchin N, Absalon J, Gurtman A, Lockhart S, et al. Safety and efficacy of the BNT162b2 mRNA Covid-19 Vaccine. N Engl J Med. 2020 Dec 31;383(27):2603,2615. doi: 10.1056/NEJMoa2034577.

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Footnote 13

Baden LR, El Sahly HM, Essink B, Kotloff K, Frey S, Novak R, et al. Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine. N Engl J Med. 2021 Feb 4;384(5):403,416. doi: 10.1056/NEJMoa2035389.

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Footnote 14

Pawlowski C, Lenehan P, Puranik A, Agarwal V, Venkatakrishnan AJ, Niesen MJM, et al. FDA-authorized mRNA COVID-19 vaccines are effective per real-world evidence synthesized across a multi-state health system. Med (N Y). 2021 Aug 13;2(8):979,992.e8. doi: 10.1016/j.medj.2021.06.007.

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Footnote 15

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.

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Footnote 16

Nasreen S, Chung H, He S, Brown KA, Gubbay JB, Buchan SA, et al. Effectiveness of mRNA and ChAdOx1 COVID-19 vaccines against symptomatic SARS-CoV-2 infection and severe outcomes with variants of concern in Ontario. medRxiv. 2021 Sep 30. doi: 10.1101/2021.06.28.21259420.

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Footnote 17

Self WH, Tenforde MW, Rhoads JP, Gaglani M, Ginde AA, Douin DJ, et al. Comparative effectiveness of Moderna, Pfizer-BioNTech, and Janssen (Johnson & Johnson) vaccines in preventing COVID-19 hospitalizations among adults without immunocompromising conditions - United States, March-August 2021. MMWR Morb Mortal Wkly Rep. 2021 Sep 24;70(38):1337,1343. doi: 10.15585/mmwr.mm7038e1.

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Footnote 18

Tang P, Hasan MR, Chemaitelly H, Yassine HM, Benslimane FM, Khatib HAA, et al. BNT162b2 and mRNA-1273 COVID-19 vaccine effectiveness against the Delta (B.1.617.2) variant in Qatar. medRxiv. 2021 Aug 11. doi: 10.1101/2021.08.11.21261885.

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Footnote 19

Higdon MM, Wahl B, Jones CB, Rosen JG, Truelove SA, Baidya A, et al. A systematic review of COVID-19 vaccine efficacy and effectiveness against SARS-CoV-2 infection and disease. medRxiv. 2021 Sep 25. doi: 10.1101/2021.09.17.21263549.

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Footnote 20

Robles Fontán MM, Nieves EG, Gerena IC, Irizarry RA. Time-varying effectiveness of three Covid-19 vaccines in Puerto Rico. medRxiv. 2021 Oct 20. doi: 10.1101/2021.10.17.21265101.

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Footnote 21

Steensels D, Pierlet N, Penders J, Mesotten D, Heylen L. Comparison of SARS-CoV-2 antibody response following vaccination with BNT162b2 and mRNA-1273. JAMA. 2021 Aug 30. doi: 10.1001/jama.2021.15125.

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Footnote 22

Richards NE, Keshavarz B, Workman LJ, Nelson MR, Platts-Mills TAE, Wilson JM. Comparison of SARS-CoV-2 antibody response by age among recipients of the BNT162b2 vs the mRNA-1273 vaccine. JAMA Netw Open. 2021 Sep 1;4(9):e2124331. doi: 10.1001/jamanetworkopen.2021.24331.

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Footnote 23

Barbeau DJ, Martin JM, Carney E, Dougherty E, Doyle JD, Dermody TS, et al. Comparative analysis of human immune responses following SARS-CoV-2 vaccination with BNT162b2, mRNA-1273, or Ad26.COV2.S. medRxiv. 2021 Sep 23. doi: 10.1101/2021.09.21.21262927.

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Footnote 24

Kaplonek P, Cizmeci D, Fischinger S, Collier A, Suscovich T, Linde C, et al. Subtle immunological differences in mRNA-1273 and BNT162b2 COVID-19 vaccine induced Fc-functional profiles. bioRxiv. 2021 Aug 31. doi: 10.1101/2021.08.31.458247.

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Footnote 25

Markewitz R, Pauli D, Dargvainiene J, Steinhagen K, Engel S, Herbst V, et al. The temporal course of T- and B-cell responses to vaccination with BNT162b2 and mRNA-1273. Clin Microbiol Infect. 2021 Sep 20. doi: 10.1016/j.cmi.2021.09.006.

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Footnote 26

Montoya JG, Adams AE, Bonetti V, Deng S, Link NA, Pertsch S, et al. Differences in IgG antibody responses following BNT162b2 and mRNA-1273 Vaccines. bioRxiv. 2021 Jun 19. doi: 10.1101/2021.06.18.449086.

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Footnote 27

Kaiser RA, Haller MC, Apfalter P, Kerschner H, Cejka D. Comparison of BNT162b2 (Pfizer-BioNtech) and mRNA-1273 (Moderna) SARS-CoV-2 mRNA vaccine immunogenicity in dialysis patients. Kidney Int. 2021 Sep;100(3):697,698. doi: 10.1016/j.kint.2021.07.004.

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Footnote 28

Stumpf J, Siepmann T, Lindner T, Karger C, Schwöbel J, Anders L, et al. Humoral and cellular immunity to SARS-CoV-2 vaccination in renal transplant versus dialysis patients: A prospective, multicenter observational study using mRNA-1273 or BNT162b2 mRNA vaccine. Lancet Reg Health Eur. 2021 Jul 23. doi: 10.1016/j.lanepe.2021.100178.

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Footnote 29

Wu AHB, Nguyen ED, Ong CM, Yun C, Lynch KL. Rate of serum SARS-CoV-2 antibody decline for two mRNA vaccines. J Appl Lab Med. 2021 Oct 14. doi: 10.1093/jalm/jfab137.

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Footnote 30

Diaz GA, Parsons GT, Gering SK, Meier AR, Hutchinson IV, Robicsek A. Myocarditis and pericarditis after vaccination for COVID-19. JAMA. 2021 Sep 28;326(12):1210,1212. doi: 10.1001/jama.2021.13443.

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Footnote 31

Albert E, Aurigemma G, Saucedo J, Gerson DS. Myocarditis following COVID-19 vaccination. Radiol Case Rep. 2021 Aug;16(8):2142,2145. doi: 10.1016/j.radcr.2021.05.033.

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Footnote 32

Tano E, San Martin S, Girgis S, Martinez-Fernandez Y, Sanchez Vegas C. Perimyocarditis in adolescents after Pfizer-BioNTech COVID-19 vaccine. J Pediatric Infect Dis Soc. 2021 Nov 11;10(10):962,966. doi: 10.1093/jpids/piab060.

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