Guidance on the use of influenza vaccine in the presence of COVID-19

November 26, 2021

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In light of the COVID-19 pandemic, the Public Health Agency of Canada (PHAC), in consultation with the National Advisory Committee on Immunization (NACI) and the Canadian Immunization Committee (CIC), has developed additional guidance on influenza vaccination. Every year, individuals with influenza and influenza-related complications increase the demand on the healthcare system in the fall and winter months. During the COVID-19 pandemic, it will be important to minimize the morbidity and mortality related to potential influenza and COVID-19 co-circulation and to reduce the burden on the Canadian health care system to enhance the capacity to respond to ongoing COVID-19 activity.

This webpage is designed to support provincial and territorial vaccine programs and primary care providers in offering influenza vaccine during the COVID-19 pandemic. The guidance on this page is based on currently available scientific evidence and expert opinion and will be updated and added to as necessary throughout the influenza season as new evidence emerges. This webpage should be considered in concert with influenza vaccine recommendations provided in the NACI Statement on Seasonal Influenza Vaccine for 2021-2022.

PHAC, in collaboration with NACI, has also released Interim guidance on continuity of immunization programs during the COVID-19 pandemic, which provides details for continuing routine immunizations and management of priority groups for immunization during the pandemic.

Delivery and administration of influenza vaccine during the COVID-19 pandemic

PHAC has released Guidance on the Delivery of Influenza Vaccination in the Presence of COVID-19 to support the delivery of influenza vaccination programs during the COVID-19 pandemic. This guidance provides additional details on:

Who should receive the influenza vaccine during the COVID-19 pandemic?

The influenza vaccine should continue to be offered to anyone 6 months of age and older who does not have contraindications to the vaccine. NACI provides a list of populations for whom annual influenza vaccination is particularly recommended.

To reduce the risk of severe illness that could potentially arise from co-infection with SARS-CoV-2 and influenza, individuals who fall into the following groups are also particularly recommended to receive the influenza vaccine:

Information on what is presently known about the clinical features of COVID-19, including presentation, comorbidities and the spectrum of disease severity, is available in the COVID-19 signs, symptoms and severity of disease: A clinician guide developed by PHAC.

Considerations for influenza vaccination during the COVID-19 pandemic

Individuals with acute symptoms of COVID-19 or an acute respiratory infection

During the COVID-19 pandemic, individuals with acute symptoms of COVID-19 or any symptoms of acute respiratory infection, including minor symptoms such as sore throat or runny nose, should postpone influenza vaccination until they have recovered, as they may unknowingly transmit COVID-19 to others and healthcare providers if they have COVID-19. Individuals with COVID-19 symptoms should visit a health care professional or call your local public health authority for information on getting tested.

Individuals currently in quarantine (self-isolation) for SARS-CoV-2 infection (COVID-19)

Individuals should postpone vaccination until their period of quarantine or isolation has ended. Vaccination should be postponed until the individual is no longer required to isolate according to criteria indicated by public health authorities in their province or territory.

Simultaneous administration with other vaccines

For people 12 years of age and older, all seasonal influenza vaccines, including live-attenuated influenza vaccine (LAIV), may be given at the same time as, or at any time before or after administration of other vaccines, including COVID-19 vaccines.

At this time, it is not recommended that children aged 5 to 11 years of age receive the COVID-19 vaccine at the same time as the influenza vaccine.

NACI currently recommends that children 5 to 11 years of age wait at least 14 days between COVID-19 vaccines and non-COVID-19 vaccines, including the influenza vaccine. This is a precautionary measure to help with determining if a side effect that may arise is due to the COVID-19 vaccine or another vaccine. Parents and caregivers of children aged 5-11 years should consult a healthcare provider if they would like their child to receive their influenza vaccine within 14 days of receiving a COVID-19 vaccine.

NACI will continue to monitor the evidence base, including ongoing and anticipated trials investigating influenza vaccines administered at the same time as, or any time before or after, COVID-19 vaccines and update its recommendations as needed. Readers should consult the current NACI guidance concerning the use of COVID-19 vaccines for updated NACI guidance and the Canadian Immunization Guide for further information on simultaneous administration of COVID-19 vaccines with other vaccines and across all eligible age groups.

Seasonal influenza vaccine safety and adverse events

Potential interference between influenza vaccine and COVID-19 disease

The hypothesis that influenza vaccine increases risk of SARS-CoV-2 infection or severe outcomes related to COVID-19 is not supported by the current evidence base.

Concerns regarding this issue emerged following the publication of a studyFootnote 1 conducted in the United States (U.S.) to explore the phenomenon of influenza vaccine interference and have not been substantiated. This study was based on U.S. Department of Defense (DoD) data from the 2017-2018 influenza season and found that the odds of seasonal coronavirus infection (SARS-CoV-2 was not assessed) were higher in individuals vaccinated with influenza vaccine compared to those who were notFootnote 1. However, further analyses conducted in response, using 7 years of data from the Canadian Sentinel Practitioner Surveillance Network (SPSN) did not find any evidence to suggest that influenza vaccine increases the risk of infections from seasonal coronaviruses (SARS-CoV-2 was not assessed)Footnote 2.

While limited data are currently available concerning the specific relationship between influenza vaccination and the likelihood of SARS-CoV-2 infection or severe outcomes related to COVID-19, evidence is emerging to suggest that influenza vaccination may have some benefits for COVID-19 prevention. A meta-analysis of 16 observational studies found that influenza vaccination was significantly associated with a lower risk of SARS-CoV-2 infection, but not significantly associated with adverse clinical outcomes, including intensive care, hospitalization, and mortalityFootnote 3.

The influenza vaccine has a longstanding safety record and is a critical tool to protect against influenza-related disease and to reduce the influenza-associated burden on the Canadian health care system, which is even more important for this influenza season, in the context of COVID-19.

Therefore, influenza vaccine should continue to be offered to everyone 6 months of age and older who does not have contraindications to the vaccine.

PHAC will continue to monitor the evidence for this phenomenon and will issue new guidance as needed.




Footnote 1

Wolff GG. (2020). Influenza vaccination and respiratory virus interference among Department of Defense personnel during the 2017-2018 influenza season. Vaccine. 38: 350-354. doi: 10.1016/j.vaccine.2019.10.005. Epub 2019 Oct 10.

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Footnote 2

Skowronski DM, Zou M, Clarke Q, Chambers C, Dickinson JA, Sabaiduc S, Olsha R, Gubbay JB, Drews SJ, Charest H, Winter AL, Jassem A, Murti M, Krajden M, De Serres G. (2020). Influenza vaccine does not increase the risk of coronavirus or other non-influenza respiratory viruses: retrospective analysis from Canada, 2010-11 to 2016-17. Clin Infect Dis. ciaa626. doi: 10.1093/cid/ciaa626. Online ahead of print.

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Footnote 3

Wang R, Liu M, Liu J. The Association between Influenza Vaccination and COVID-19 and Its Outcomes: A Systematic Review and Meta-Analysis of Observational Studies. Vaccines (Basel) 2021 May 20;9(5):10.3390/vaccines9050529.

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