Addendum to the guidance on the use of COVID-19 vaccines in the fall of 2023

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Organization: Public Health Agency of Canada

Date published: September 12, 2023

Pub.: 230368

Publication date: September 12, 2023

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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.

Use of the XBB.1.5-containing formulation

For additional details, please see NACI Guidance on the use of COVID-19 vaccines in the fall of 2023.

Epidemiology and the XBB.1.5-containing COVID-19 vaccine

Use of the XBB.1.5-containing COVID-19 vaccines

Considerations for those who have been previously vaccinated (i.e. completed a primary series)

Considerations for those not previously vaccinated

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

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, oruncertainty 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, R Krishnan, K Young, MC Tunis, R Harrison, S Wilson, and S Deeks, on behalf of NACI.

NACI gratefully acknowledges the contribution of: J Daniel, K Ramotar, C Mauviel, M Salvadori, SH Lim, and the NACI Secretariat.

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, M O’Driscoll, J Papenburg, A Pham-Huy, B Sander, and S Wilson.

Liaison representatives:  L Bill / M Nowgesic (Canadian Indigenous Nurses Association), LM Bucci (Canadian Public Health Association), S Buchan (Canadian Association for Immunization Research and Evaluation), E Castillo (Society of Obstetricians and Gynaecologists of Canada), J Comeau (Association of Medical Microbiology and Infectious Disease Canada), M Lavoie (Council of Chief Medical Officers of Health), J MacNeil (Centers for Disease Control and Prevention, United States), D Moore (Canadian Paediatric Society), M Naus (Canadian Immunization Committee), M Osmack (Indigenous Physicians Association of Canada), J Potter (College of Family Physicians of Canada), 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), P Fandja (Marketed Health Products Directorate, Health Canada), M Su (COVID-19 Epidemiology and Surveillance, PHAC), S Ogunnaike-Cooke (CIRID, PHAC), C Pham (Biologic and Radiopharmaceutical Drugs Directorate, Health Canada), M Routledge (National Microbiology Laboratory, PHAC), and T Wong (First Nations and Inuit Health Branch, Indigenous Services Canada).

NACI COVID-19 Vaccine Working Group

Members:S Wilson (Chair), M Adurogbangba, M Andrew, M Baca-Estrada, Y-G Bui, H Decaluwe, P De Wals, V Dubey, S Hosseini-Moghaddam, M Miller, D Moore, M Wallace, and J Regan.

PHAC participants:E Abrams, P Doyon-Plourde, N Forbes, M Hersi, N Islam, SJ Ismail, C Jensen, R Krishnan, SH Lim, R Neves Miranda, J Montroy, R Pless, M Salvadori, E Tice, A Tuite, MC Tunis, B Warshawsky, E Wong, R Ximenes, K Young, and J Zafack.


Footnote a

It should be noted that booster vaccination using shorter intervals (i.e. 3 months to < 6 months) following  previous vaccination or infection has not been shown to pose a safety risk, though evidence shows that the antibody response is higher with longer intervals between infection and vaccination and with longer intervals between vaccination doses

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Footnote b

Autonomous decisions should be made by Indigenous Peoples with the support of healthcare and public health partners in accordance with the United Nations Declaration on the Rights of Indigenous Peoples.

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References 1

Public Health Agency of Canada. COVID-19 epidemiology update: Testing and variants. Data cut-off 2023 Aug 20 [Internet]. Ottawa (ON): Health Canada; 2023 Aug 29 [cited 2023 Aug 30]. Available from:

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References 2

Moderna Inc. Moderna COVID-19 Variant Vaccines [slides presented at Vaccines and Related Biological Products Advisory Committee (VRBPAC) meeting June 15, 2023] [Internet]. Silver Spring (MD): Food and Drug Administration (FDA); 2023 Jun 15 [cited 2023 Jul 17]. Available from:

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