Archived 37: Updated guidance on a first booster dose of COVID-19 vaccines in Canada [2022-04-12]

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Publication: April 12, 2022

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Organization: Public Health Agency of Canada

Published: 2022-04-12

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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.


On September 28, 2021, NACI published guidance on booster COVID-19 vaccine doses in long-term care residents and seniors living in other congregate settings. On October 29, 2021, NACI published interim guidance on booster COVID-19 vaccine doses in Canada. On December 3, 2021, NACI published updated guidance on booster COVID-19 vaccine doses in Canada for adults 18 years of age and older. The recommendations on booster doses of COVID-19 vaccines were reviewed and reaffirmed in the context of the Omicron (B.1.1.529) variant of concern (VOC) on December 14, 2021. Since that time:

NACI continues to monitor rapidly evolving scientific data recognizing that the trajectory of the COVID-19 pandemic remains unclear.

NACI's recommendations are aligned with the goals of the Canadian COVID-19 Pandemic Response that were updated on February 14, 2022:


NACI's recommendations on booster doses are based on the decision-making framework outlined in the published statement entitled Interim guidance on booster COVID-19 vaccine doses in Canada (October 29, 2021). Recommendations are based on evidence of the need for (e.g., evidence of decreased vaccine effectiveness against severe illness and/or infection depending on the population) and benefit of (e.g., safety and effectiveness) a booster dose in the Canadian context.

On March 1 and March 22, 2022, NACI reviewed data on the current epidemiology of COVID-19 nationally and internationally, along with additional evidence included in published scientific literature and preprints, regarding the duration of protection from a COVID-19 vaccine primary series and the efficacy and/or effectiveness and safety of a first booster dose (i.e., third dose in most individuals) for adults and adolescents. Additionally, NACI reviewed the manufacturer's clinical data available in the regulatory submission to Health Canada to support the expanded indication of Pfizer-BioNTech Comirnaty (30 mcg) as a booster dose among individuals 16 to 17 years of age. NACI approved these updated recommendations on April 6, 2022.

For further information on NACI's recommendations on the use of COVID-19 vaccines, please refer to National Advisory Committee on Immunization (NACI): Statements and publications and the COVID-19 vaccine chapter in the Canadian Immunization Guide (CIG).

Further information on NACI's process and procedures is available elsewhere.Footnote 1Footnote 2


NACI's updated recommendations on the use of a first booster dose of COVID-19 vaccine in Canada are presented below, with additional considerations on when to offer the booster dose in light of the current context of the pandemic.

NACI continually assesses the evidence and evaluates recommendations in light of this evidence. Based on strong accumulated real-world evidence, NACI's recommendation for a first booster dose in adults 18 to 49 years (published December 3, 2021) has been strengthened from "discretionary" to "strong." NACI's recommendation for a first booster dose in adolescents 12 to 17 years of age (published January 28, 2022) who may be at higher risk of severe outcomes from COVID-19 infection has also been strengthened from "discretionary" to "strong". NACI has also added a new "discretionary" recommendation for a first booster dose in all other adolescents.

Please see Table 1 for an explanation of strong versus discretionary NACI recommendations.

With NACI's updated recommendations, a first booster dose may now be offered to everyone 12 years of age and over. Given the current resurgence in cases due to the increased transmissibility of the Omicron BA.2 sub-lineage and the lifting of public health measures, NACI's updated recommendations may help to further reduce infections and severe disease. Protection is highest soon after the booster dose is given.

NACI continues to strongly reiterate previous evidence-informed recommendations for the primary series of COVID-19 vaccines in the authorized age groups. Additional details are available in the COVID-19 vaccine chapter in the Canadian Immunization Guide and NACI Statements and publicationsTable 2).

Details on options and considerations for vaccine types and timing of administration among certain adult populations for the primary series and booster dose were last updated in Table 4 of NACI statement: Recommendations on the use of Medicago COVID-19 vaccine (Covifenz).

  1. NACI recommendation for a first booster dose of COVID-19 vaccine in adults:

    NACI recommends that a first booster dose of an authorized COVID-19 vaccineFootnote 1Footnote 2 should be offered ≥6 months after completion of a primary COVID-19 vaccine series to adults ≥18 years of age. An mRNA COVID-19 vaccine dose is preferred for the booster dose.

    (Strong NACI recommendation)
  1. NACI recommendations for a first booster dose of COVID-19 vaccine in adolescents:

    1. 2.1 For the following groups, the NACI recommendation has been strengthened from "discretionary" to "strong". NACI now recommends that a booster dose of an mRNA COVID-19 vaccineFootnote 3 should be offered ≥6 months after completion of a primary COVID-19 vaccine series to adolescents 12 to 17 years of age:

The above-mentioned adolescents may experience biological and/or social risk factors that may intersect, and some may experience systemic barriers to accessing health care.

For all other adolescents, a new recommendation has been added:

  1. 2.2 NACI recommends that a booster dose of an mRNA COVID-19 vaccineFootnote 3 may be offered ≥6 months after completion of a primary COVID-19 vaccine series to all other adolescents 12 to 17 years of age in the context of heightened (ongoing or novel) epidemiological risk.

    (Discretionary NACI recommendation)

Considerations on when to offer the first booster dose:

NACI continues to monitor and assess the evidence as it emerges and will update its recommendations as needed.

Summary of evidence

Evolving epidemiology

Coverage and protection from recent infection

Vaccine effectiveness (VE) against infection and/or symptomatic disease over time following a primary series

VE against outcomes of clinical importance including severe disease over time following a primary series

Vaccine effectiveness over time following a first booster

Safety of a first booster dose

Ethics, equity, feasibility, and acceptability (EEFA)

Other considerations

Research priorities

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
Wording "should/should not be offered" "may/may not be offered"
Rationale Known/anticipated advantages outweigh known/anticipated disadvantages ("should"), or 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
Implication 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 be considered for some populations/individuals in some circumstances. Alternative approaches may be reasonable.


This statement was prepared by: E Wong, B Warshawsky, N Forbes, J Zafack, SJ Ismail, J Montroy, A Nunn, R Stirling, M Salvadori, MC Tunis, B Sander, R Harrison, and S Deeks, on behalf of NACI.

NACI gratefully acknowledges the contribution of: N. St. Pierre, K Ramotar, SH Lim, E Terrataca, L Coward, R Krishnan, and C Jensen

NACI members: S Deeks (Chair), R Harrison (Vice-Chair), M Andrew, J Bettinger, N Brousseau, H Decaluwe, P De Wals, E Dubé, V Dubey, K Hildebrand, K Klein, J Papenburg, A Pham-Huy, B Sander, S Smith, and S Wilson.

Liaison representatives: L Bill / M Nowgesic (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, United States), L Dupuis (Canadian Nurses Association), D Fell (Canadian Association for Immunization Research and Evaluation), S Funnell (Indigenous Physicians Association of Canada), J Hu (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), 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 (COVID-19 Epidemiology and Surveillance, PHAC), 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: R Harrison (Chair), N Brousseau, Y-G Bui, S Deeks, K Dooling, K Hildebrand, M Miller, M Murti, J Papenburg, D Smith, and S Vaughan.

PHAC participants: NK Abraham, N Alluqmani, L Coward, N Forbes, C Jensen, CY Jeong, A Jirovec, A Killikelly, R Krishnan, SH Lim, N Mohamed, J Montroy, A Nam, S Pierre, R Pless, M Salvadori, A Sinilaite, A Stevens, R Stirling, E Tice, A Tuite, MC Tunis, B Warshawsky, E Wong, R Ximenes, MW Yeung, J Zafack.

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