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

September 23, 2022

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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 2022-2023.

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 groups for whom 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

Every appropriate opportunity to vaccinate against influenza should be taken. Vaccination against influenza remains the most effective way to prevent influenza illness and influenza-related complications, and is an important component of managing health care system capacity during the influenza season in the context of any ongoing COVID-19 activity.

Individuals with symptomatic COVID-19 or asymptomatic SARS-CoV-2 infection

Individuals with COVID-19 or asymptomatic SARS-CoV-2 infection should not leave isolation solely to be vaccinated against influenza. In the outpatient setting vaccination should be deferred until the end of the isolation period as these individuals may transmit COVID-19 to others, including healthcare providers. In the inpatient or congregate living setting, individuals with COVID-19 or asymptomatic SARS-CoV-2 infection can be vaccinated against influenza, with appropriate infection prevention and control measures in place. In all scenarios, given the optimal timing of influenza vaccination for individuals with COVID-19 is still unknown, consideration can be given to deferring vaccination until the resolution of acute illness.

Individuals with symptoms of an acute respiratory infection

Individuals with symptoms of acute respiratory infection can be vaccinated against influenza. However, in the outpatient setting, vaccination should be deferred until the resolution of symptoms, given the possibility of unknowingly transmitting COVID-19 or other respiratory infections to others, including healthcare providers. A symptomatic patient who presents to an outpatient setting may be vaccinated at the discretion of the clinic. Individuals in inpatient or congregate living settings with acute respiratory infection symptoms can be vaccinated against influenza, with appropriate infection prevention and control measures in place. More information on vaccinating individuals during acute illness can be found in the Canadian Immunization Guide’s section on Contraindications and precautions associated with specific conditions: Acute Illness.

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

Individuals in quarantine for COVID-19 or asymptomatic SARS-CoV-2 infection can be vaccinated against influenza but should not leave quarantine solely to do so. In the outpatient setting, vaccination should be deferred until the end of the quarantine period given the possibility of unknowingly transmitting COVID-19 to others, including healthcare providers. An individual in quarantine who presents to an outpatient setting may be vaccinated at the discretion of the clinic. In the inpatient or congregate living setting, individuals in quarantine can be vaccinated against influenza.

Concurrent administration with other vaccines

For people 5 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 6 months to 5 years of age routinely receive the COVID-19 vaccine at the same time as the influenza vaccine. NACI currently recommends that children 6 months to 5 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 prevent erroneous attribution of adverse events following immunization to one particular vaccine or the other. Parents and caregivers of children aged 6 months to 5 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 Canadian Immunization Guide chapter on COVID-19 vaccine for updated NACI guidance and for further information on concurrent administration of COVID-19 vaccines with other vaccines across all eligible age groups.

Seasonal influenza vaccine: Benefits, safety and adverse events

Potential association between influenza vaccine and SARS-CoV-2 infection

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, which have not been substantiated, emerged following the publication of a studyFootnote 1 conducted in the United States (U.S.) to explore the phenomenon of influenza vaccine interference. 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, an analysis 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. A number of studies have since been published that show that rather than increase the risk of SARS-CoV-2 infection, influenza vaccine may instead reduce the risk of SARS-CoV-2 infection Footnote 3Footnote 4Footnote 5Footnote 6Footnote 7Footnote 8Footnote 9Footnote 10Footnote 11Footnote 12Footnote 13Footnote 14Footnote 15Footnote 16Footnote 17. Further research is needed to better understand the specific relationship between influenza vaccination and the likelihood of SARS-CoV-2 infection, and whether influenza vaccine also reduces the severity of and/or risk of serious outcomes due to COVID-19.

The influenza vaccine has a longstanding safety record and is a critical tool to protect against influenza-related disease and 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.

References

Footnotes

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. Influenza Vaccine Does Not Increase the Risk of Coronavirus or Other Noninfluenza Respiratory Viruses: Retrospective Analysis From Canada, 2010-2011 to 2016-2017. Clin Infect Dis. 2020 Nov 19;71(16):2285-2288. doi: 10.1093/cid/ciaa626.

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Footnote 3

Yang MJ, Rooks BJ, Le TTT, Santiago IO, Diamond J, Dorsey NL, et al. Influenza Vaccination and Hospitalizations Among COVID-19 Infected Adults. J Am Board Fam Med. 2021 Feb;34(Supplement):S179–82.

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Footnote 4

Wilcox CR, Islam N, Dambha-Miller H. Association between influenza vaccination and hospitalisation or all-cause mortality in people with COVID-19: a retrospective cohort study. BMJ Open Resp Res. 2021 Mar;8(1):e000857.

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Footnote 5

Umasabor-Bubu OQ, Bubu OM, Mbah AK, Nakeshbandi M, Taylor TN. Association between Influenza Vaccination and severe COVID-19 outcomes at a designated COVID-only hospital in Brooklyn. American Journal of Infection Control. 2021 Apr;S0196655321002017.

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Footnote 6

Taghioff SM, Slavin BR, Holton T, Singh D. Examining the potential benefits of the influenza vaccine against SARS-CoV-2: A retrospective cohort analysis of 74,754 patients. PLoS ONE. 2021 Aug 3;16(8):e0255541.

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Footnote 7

Su W, Wang H, Sun C, Li N, Guo X, Song Q, et al. The Association Between Previous Influenza Vaccination and Coronavirus Disease 2019 Infection Risk and Severity: A Systematic Review and Meta-Analysis. American Journal of Preventive Medicine. 2022 Mar;S0749379722001313.

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Footnote 8

Sánchez-García C, Salinas-Aguirre JE, Rodríguez-Muñoz L, Rodríguez-Sánchez R, Díaz-Castaño A, Bernal-Gómez R. History of influenza immunization in COVID-19 patients: impact on mortality. GMM. 2021 Jun 14;157(1):6504.

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Footnote 9

Paganoti C de F, Rodrigues AS, Francisco RPV, Costa RA da. The Influenza Vaccine May Protect Pregnant and Postpartum Women against Severe COVID-19. Vaccines. 2022 Jan 28;10(2):206.

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Footnote 10

Kowalska M, Niewiadomska E, Barański K, Kaleta-Pilarska A, Brożek G, Zejda JE. Association between Influenza Vaccination and Positive SARS-CoV-2 IgG and IgM Tests in the General Population of Katowice Region, Poland. Vaccines. 2021 Apr 21;9(5):415.

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Footnote 11

Huang K, Lin SW, Sheng WH, Wang CC. Influenza vaccination and the risk of COVID-19 infection and severe illness in older adults in the United States. Sci Rep. 2021 Dec;11(1):11025.

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Footnote 12

Green I, Ashkenazi S, Merzon E, Vinker S, Golan-Cohen A. The association of previous influenza vaccination and coronavirus disease-2019. Human Vaccines & Immunotherapeutics. 2021 Jul 3;17(7):2169–75.

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Footnote 13

Erismis B, Karabela SN, Eksi F, Karandere F, Dogan B, Okay F, et al. Annual influenza vaccination effect on the susceptibility to COVID-19 infection. Cent Eur J Public Health. 2021 Mar 31;29(1):14–7.

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Footnote 14

Conlon A, Ashur C, Washer L, Eagle KA, Hofmann Bowman MA. Impact of the influenza vaccine on COVID-19 infection rates and severity. American Journal of Infection Control. 2021 Jun;49(6):694–700.

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Footnote 15

Chen AT, Stacey HD, Marzok A, Singh P, Ang J, Miller MS, et al. Effect of Inactivated Influenza Vaccination on Human Coronavirus Infection: Secondary Analysis of a Randomized Trial in Hutterite Colonies. Vaccine. 2021 Oct;S0264410X21013414.

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Footnote 16

Bozek A, Kozłowska R, Galuszka B, Grzanka A. Impact of influenza vaccination on the risk of SARS-CoV-2 infection in a middle-aged group of people. Human Vaccines & Immunotherapeutics. 2021 Apr 29;1–5.

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Footnote 17

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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