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The World Health Organization (WHO) has officially released its guidelines for the composition of influenza vaccines intended for the 2025 influenza season in the southern hemisphere. This announcement was made during an informational session following a four-day meeting focused on Influenza Virus Vaccine Composition, which occurs biannually—once for each hemisphere.
These consultations are organized by WHO in collaboration with a panel of experts from WHO Collaborating Centres and Essential Regulatory Laboratories. They analyze data from the WHO Global Influenza Surveillance and Response System (GISRS) to inform their recommendations. These guidelines serve as a foundation for national vaccine regulatory authorities and pharmaceutical companies to formulate, produce, and approve influenza vaccines for upcoming seasons.
Due to the ever-changing nature of influenza viruses that infect humans, it is crucial to periodically update the viral strains included in vaccines to ensure their effectiveness.
Recommended Vaccine Components
The WHO advises that trivalent vaccines designed for use during the 2025 southern hemisphere influenza season should include:
Egg-based Vaccines
- 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.
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;
- A B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
The recommendation regarding the B/Yamagata lineage component within quadrivalent influenza vaccines remains consistent with prior guidelines:
- A B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.
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