WORLD NEWS
H3N2 subclade K evaded antibodies, but neutralisation rose after vaccination
The H3N2 subclade K that spread in 2025 entered some cell lines more efficiently and escaped existing antibodies, yet neutralising activity in human serum rose significantly after vaccination. The September 4 study linked much of both behaviour to the A186D change in haemagglutinin.
This is not proof that vaccination prevents every infection. Researchers used particles bearing influenza surface proteins to measure cell entry and antibody neutralisation in the laboratory; they did not follow people for infection, hospitalisation or death.
What was compared?
The team compared vaccine-matched H3N2 proteins with late-2025 subclade K proteins across cell lines and paired serum collected before and after vaccination.
What did it find?
K entered selected cells more efficiently and resisted pre-vaccination antibodies, while vaccination markedly raised neutralising titres. The paper does not convert that rise into a clinical protection percentage.
Why does A186D matter?
Reversing A186D reduced both enhanced entry and antibody escape, suggesting one haemagglutinin change affects receptor use and antigenic shape. It is not the sole determinant of disease.
What should people do?
The result does not justify choosing a product independently or dropping other precautions. Real effectiveness varies by age, health, timing and circulating viruses; follow current national guidance.
What comes next?
Surveillance and real-world effectiveness studies must test whether laboratory neutralisation translates into fewer infections and severe outcomes. WHO composition updates remain the official reference.