The World Health Organization has recommended updating all three viral strains included in influenza vaccines for the Northern Hemisphere’s 2026 flu season.
The changes include two influenza A strains and one influenza B strain, including a new A(H3N2) variant known as subclade K that began spreading in late 2025, according to a Feb. 27 news release. The variant has been linked to earlier and more intense outbreaks and was expected to dominate flu transmission. Current vaccines offered only partial protection against the strain, raising concerns about reduced effectiveness.
An interim Canadian study found the current vaccine was 37% effective against subclade K and 40% effective against A(H3N2) overall. The WHO’s strain recommendations vary by manufacturing method. A/Missouri/11/2025 (H1N1) and either A/Darwin/1454/2025 or A/Darwin/1415/2025 (H3N2) are included in all formulations. The B component varies between B/Tokyo/EIS13-175/2025 and B/Pennsylvania/14/2025.
Subclade K emerged during a flu season marked by rising hospitalizations and declining vaccination rates. By late November, nearly 5,000 flu hospitalizations were reported in a single week in the U.S., and vaccination rates had fallen 8% compared to 2024.
The FDA’s vaccine advisory panel is scheduled to meet March 12 to consider whether to adopt the WHO’s recommendations for U.S. flu shots.
The post WHO recommends new strains for 2026 flu shots appeared first on Becker's Hospital Review | Healthcare News & Analysis.
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