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

September 29, 2020

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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 2020-2021.

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

Delivery and administration of influenza vaccine during 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 fall. This guidance provides additional details on:

Who should receive the influenza vaccine during 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 this fall:

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

Individuals with symptoms of an acute respiratory infection

During the COVID-19 pandemic, individuals with any symptoms of acute respiratory infection, including minor symptoms such as sore throat or runny nose, should defer influenza vaccination until they have recovered, as they can pose an unnecessary risk 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 with suspected, probable or confirmed COVID-19

Individuals with suspected, probable, or confirmed COVID-19 and those who are close contacts of a case should defer influenza vaccination during their period of quarantine or isolation. Vaccination should be deferred until the individual is no longer required to isolate according to criteria indicated by public health authorities in their province or territory.

Seasonal influenza vaccine safety and adverse events

Potential interference between influenza vaccine and COVID-19 disease

The possibility of influenza vaccine to increase the risk of infection with coronavirus or other non-influenza respiratory diseases was presented in a recent study from the United States (US) by Wolff et al. published in January 2020. The study was conducted using data from the 2017-2018 influenza season, before the COVID-19 pandemicFootnote 1. It found the odds of seasonal coronavirus infection (the study did not assess SARS-CoV-2) were higher in individuals vaccinated with influenza vaccine compared to those who were not. However, a recent Canadian study by Skowronski et al.Footnote 2, conducted in response to the Wolff et al. study, provided a test-negative design analysis of 7 years of data from the Canadian Sentinel Practitioner Surveillance Network (SPSN). This study showed no evidence that influenza vaccine increased the risk of infections from seasonal coronaviruses. This study also did not assess SARS-CoV2. The authors of the Canadian study also identified significant methodological flaws in the design of the Wolff et al. studyFootnote 2.

A thorough literature review conducted by PHAC to identify studies examining the question of influenza vaccine and risk of COVID-19 infection found few results (2 studies specific to COVID-19) that were of low quality. The studies that were identified which looked at other coronaviruses were also of low quality and had conflicting findings.

Taken together, the hypothesis that influenza vaccine increases the risk of SARS-CoV-2 infection is not supported by the current evidence base. 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 evidence for this phenomenon and will issue new guidance as needed.

Resources

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. (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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