Subclade K, the sequel: 2025/26 influenza vaccine effectiveness findings from Canada

Summary: In an October 2025 pre-season risk assessment, Canadian investigators used global genomic and antigenic surveillance data to highlight important mutations in circulating influenza A(H3N2) viruses, including glycosylation changes affecting antigenic site A and major substitutions affecting antigenic site B. Ongoing viral evolution culminated in sweeping predominance of subclade K, an antigenically distinct variant showing early surge in Europe and elsewhere, leading to further threat assessments and vaccine mismatch concerns expressed by others. Here, the Canadian Sentinel Practitioner Surveillance Network (SPSN) provides interim estimates of 2025/26 influenza vaccine effectiveness (VE), including genotypic and phenotypic characterization of contributing case viruses with immuno-epidemiological considerations for subclade K protection. Presenter: Danuta Skowronski MD, FRCPC Dr. Danuta Skowronski is national lead of the Canadian Sentinel Practitioner Surveillance Network (SPSN) that undertakes community-based respiratory virus surveillance and vaccine effectiveness (VE) monitoring including integrated genetic and epidemiological evaluations. With 200 peer-reviewed publications, Dr. Skowronski has contributed major insights into the determinants of influenza vaccine performance, including molecular-level vaccine-virus relatedness, repeat vaccination and imprinting effects.

BC CDC Presenters

2/17/2026 8:00:00 PM