“All three virus components of 2026-2027 U.S. seasonal flu vaccines were updated compared to those used for 2025-2026 U.S. seasonal flu vaccines.”
2026-2027 Flu Seasoncdc.govStraight from CDC's season page, updated Sept. 29: every strain in this year's shot is new, including one for the H3N2 subclade K that spread widely last season.