Flu Shots Crucial as Canada Faces Potential Surge in Mutating Strains

As of November 14th, 2025, Canada is bracing for a potentially more severe flu season, with health experts warning that the dominant strain of influenza is mutating. According to infectious diseases specialist Dr. Isaac Bogoch, this could mean the annual flu shot may be a "slight mismatch" for the mutated strain. However, Bogoch emphasizes that getting the flu shot is still crucial, as it will provide protection against the other circulating strains and offer some level of protection against the mutating strain.

The University of Toronto Department of Medicine professor explains that there are three influenza strains that typically circulate in the winter, with one of the influenza A strains, H3N2, being of particular concern as it appears to be evolving. While the vaccine may have reduced efficacy against this mutating strain, it will still work reasonably well against the other two strains.

Recent data from the federal government and Public Health Ontario shows that flu cases are already rising in Canada, with the majority of cases being influenza A. Health officials are projecting an increase in influenza activity in the coming weeks. In Alberta, the first flu-related death of the season has already been reported, following the province's deadliest influenza season in more than a decade last year.