U.S. 2026-2027 flu vaccines updated on all three virus strains

CDC says all three virus strains in 2026-2027 U.S. flu vaccines were updated from 2025-2026, including new A/Missouri/11/2025 (H1N1) and A/Darwin/1454/2025 components for egg-based shots. Vaccines cover ages 6 months and older, with September-October as ideal timing for single-dose recipients. I see this full reset as raising the stakes on matching circulating viruses.