Antibody titers elicited by the current inactivated influenza vaccine were modest against #Influenza A(H3N2) subclade K compared to responses against prior H1N1 and H3N2 strains.

Lower baseline and postvaccination titers to subclade K suggest partial immune evasion, raising implications for continued transmission and the selection of upcoming influenza vaccine strains.

This cohort study examines antibody responses to influenza A(H3N2) subclade K and other strains before and after vaccination against influenza.