WHO Influenza Vaccine Composition and Surveillance Updates 2025-2026
- Food and Drug Administration (FDA) have established the recommended compositions for influenza vaccines for the 2025-2026 northern hemisphere influenza season.
- For the 2025-2026 season, all influenza vaccines in the United States will be trivalent.
- The specific virus strains recommended by the WHO vary depending on the manufacturing process used for the vaccine.
The World Health Organization (WHO) and the U.S. Food and Drug Administration (FDA) have established the recommended compositions for influenza vaccines for the 2025-2026 northern hemisphere influenza season. These recommendations are designed to align vaccine formulations with the circulating strains of the virus to maximize public health protection.
For the 2025-2026 season, all influenza vaccines in the United States will be trivalent. This means they are formulated to protect against three primary seasonal influenza viruses: one A(H1N1) virus, one A(H3N2) virus, and one B/Victoria lineage virus.
Vaccine Composition Details
The specific virus strains recommended by the WHO vary depending on the manufacturing process used for the vaccine. For egg-based vaccines, the recommended components for the 2025-2026 northern hemisphere season include:
- An A/Victoria/4897/2022 (H1N1)pdm09-like virus
- An A/Croatia/10136RV/2023 (H3N2)-like virus
- A B/Austria/1359417/2021 (B/Victoria lineage)-like virus
For vaccines produced via cell culture, recombinant protein, or nucleic acid-based methods, the WHO recommends a different set of components:
- An A/Wisconsin/67/2022 (H1N1)pdm09-like virus
- An A/District of Columbia/27/2023 (H3N2)-like virus
- A B/Austria/1359417/2021 (B/Victoria lineage)-like virus
the recommendation for the B/Yamagata lineage component remains unchanged for quadrivalent influenza vaccines, specifying a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.
Regulatory Updates and Administration
The FDA provided its recommendations to update the composition of 2025-2026 U.S. Influenza vaccines on March 13, 2025. The CDC recommends seasonal flu vaccination for adults, pregnant women, and children, specifically noting the use of single-dose formulations that are free of thimerosal as a preservative.
Recent regulatory approvals have expanded the available options for vaccination. In March 2025, the FDA approved FluBlok, a recombinant influenza vaccine, for individuals aged 9 years and older; previously, the approval was limited to those aged 18 years and older.
in September 2024, the FDA approved FluMist, a live attenuated influenza vaccine, for administration by either a caregiver or the patient themselves.
Global Surveillance and Timing
The WHO coordinates vaccine composition meetings twice annually to address the different needs of the Northern and Southern Hemispheres. Recommendations for the Northern Hemisphere are typically released in February, while Southern Hemisphere recommendations are released in September.
The Northern Hemisphere recommendation for the trivalent vaccine was released on February 28, 2025, and was noted to be the same as the recommendations for the Southern Hemisphere.
These efforts are part of a broader strategy by the Global Influenza Programme to provide Member States with technical support and coordination. This includes the development of candidate vaccine viruses and potency testing reagents to prepare health systems against seasonal, zoonotic, and pandemic influenza threats.
Looking forward, the WHO has already listed February recommendations for the 2026-2027 northern hemisphere season and September recommendations for 2026 in the Southern hemisphere as part of its ongoing surveillance and planning cycle.