An interim analysis published in Eurosurveillance estimates that the COVID-19 vaccine for the 2025/26 season reduced the risk of illness in Canada by about half at about 9 weeks after vaccination, offering protection beyond the vaccine’s target strain.

Seasonal COVID-19 vaccination is recommended in Canada as in several other countries for people older than 6 months with an increased risk of severe illness from the infection, and for all adults aged 65 or older. In the 2025/26 respiratory virus season, the vaccine was updated to target the LP.8.1 strain as recommended by the World Health Organization (WHO), but other strains were also circulating during that period.

Estimating vaccine effectiveness during a challenging respiratory season

The research was conducted through the Canadian Sentinel Practitioner Surveillance Network, which sought to perform an early estimate of COVID-19 vaccine effectiveness for the 2025/26 season and to explore the effect that influenza and other respiratory infections might have on these estimates.