Guidance on the use of influenza vaccine in the presence of COVID-19
February 6, 2023
On this page
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 .
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 .
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:
- People with 
- People capable of transmitting influenza to those at high risk of severe illness related to COVID-19
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  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 Guides section on .

# 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 6 months 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.
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  for updated NACI guidance and for further information on  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 study 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 not. 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). 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 . 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.