Influenza vaccine effectiveness from nine studies during drifted A(H3N2) subclade K predominance, Europe, September 2025 to January 2026 - PubMed
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- #A(H3N2)
- #influenza
- The 2025/26 European influenza season was dominated by the A(H3N2) virus, with most sequenced viruses belonging to subclade K, which was genetically drifted from the vaccine virus.
- Vaccine effectiveness (VE) estimates from nine European studies across 19 countries showed all-age influenza A VE of 25-45% for outpatient and hospital settings combined.
- The highest VE estimates were among children, ranging from 47-72%.
- Despite genetic drift, VE was similar to other seasons, suggesting vaccination should still be encouraged.
- The study recommends complementing vaccination with other infection prevention and control measures.