WHO announces recommended viral composition for 2025 flu vaccines

The World Health Organization (WHO) today announced its recommendations for the viral composition of influenza vaccines for the 2025 influenza season in the southern hemisphere. The announcement was made during a briefing after a 4-day meeting on the composition of influenza virus vaccines. The meeting takes place twice a year, once for the southern hemisphere and once for the northern hemisphere.

WHO is organizing these consultations with an advisory group of experts meeting at WHO Collaborating Centers and WHO Core Regulatory Laboratories to analyze influenza virus surveillance data generated by the Global Surveillance System WHO Influenza and Response System (GISRS). The recommendations issued are used by national vaccine regulatory agencies and pharmaceutical companies to develop, produce and license influenza vaccines for the following influenza season.

Periodic updating of viruses in influenza vaccines is necessary for vaccines to be effective due to the constantly evolving nature of influenza viruses, including those that circulate and infect humans.

WHO recommends that trivalent vaccines intended for use during the 2025 influenza season in the southern hemisphere contain the following:

Egg-based vaccines

• an A/Victoria/4897/2022 (H1N1)pdm09 type virus;
• a virus type A/Croatia/10136RV/2023 (H3N2); And
• a type B/Austria/1359417/2021 virus (B/Victoria lineage).

Vaccines based on cell cultures, recombinant proteins or nucleic acids

• a virus type A/Wisconsin/67/2022 (H1N1)pdm09;
• a type A/District of Columbia/27/2023 (H3N2) virus; And
• a type B/Austria/1359417/2021 virus (B/Victoria lineage).

The recommendation for the B/Yamagata lineage component of quadrivalent influenza vaccines remains unchanged from previous recommendations:

• a type B/Phuket/3073/2013 virus (B/Yamagata lineage).