The FDA has issued recommendations for the influenza virus strains to be included in vaccines for the 2025 to 2026 U.S. flu season following a comprehensive review of domestic and global surveillance data. In collaboration with the CDC and DoD, the agency evaluated circulating influenza strains, mid-season vaccine effectiveness data from 2024 to 2025, and available candidate vaccine strains. The FDA does not anticipate delays in vaccine availability, and the selected strains are consistent with prior formulations.
Trivalent seasonal influenza vaccines for the upcoming season will include two influenza A subtype viruses (H1N1 and H3N2) and one influenza type B virus. For egg-based vaccines, the recommended strains are an A/Victoria/4897/2022 (H1N1)pdm09-like virus; an A/Croatia/10136RV/2023 (H3N2)-like virus; and a B/Austria/1359417/2021 (B/Victoria lineage)-like virus. For cell- or recombinant-based vaccines, the selected strains are an A/Wisconsin/67/2022 (H1N1)pdm09-like virus; an A/District of Columbia/27/2023 (H3N2)-like virus; and a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
The strain selection process was informed by an interagency meeting on March 13, 2025, where representatives from the FDA, CDC, and DoD reviewed epidemiologic and antigenic data. The discussion included global influenza surveillance, mid-season vaccine effectiveness assessments, and candidate strain evaluations. The final strain selection aligns with current circulating patterns and is expected to provide adequate protection.
The FDA has communicated these recommendations to manufacturers of FDA-approved seasonal influenza vaccines and anticipates a sufficient vaccine supply for the 2025 to 2026 influenza season. Meeting materials, including surveillance reports and data informing strain selection, are publicly available through federal health agencies.
Reference: U.S. Food and Drug Administration. Influenza vaccine composition for the 2025-2026 U.S. influenza season. Published March 13, 2025. Accessed March 14, 2025. https://www.fda.gov/vaccines-blood-biologics/influenza-vaccine-composition-2025-2026-us-influenza-season
