Composition of Influenza Virus vaccine for the 2025 southern hemisphere

Introduction
The periodic replacement of viruses contained in influenza vaccines is necessary in order for the vaccines to be effective due to the constant evolving nature of influenza viruses, including those circulating and infecting humans.

Twice annually, WHO organizes consultations to analyse influenza virus surveillance data generated by the WHO Global Influenza Surveillance and Response System (GISRS), and issues recommendations on the composition of the influenza vaccines for the following influenza season.

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

Egg-based vaccines
- 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.

Cell culture-, recombinant protein- or nucleic acid-based vaccines
- 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 recommendation for the B/Yamagata lineage component of quadrivalent influenza vaccines remains unchanged from previous recommendations: - a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.

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