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.
The WHO recommends that trivalent vaccines for use in the 2024-2025 northern hemisphere influenza season contain the following:
Egg-based vaccines - an A/Victoria/4897/2022 (H1N1)pdm09-like virus;
- an A/Thailand/8/2022 (H3N2)-like virus; and
- a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
Cell culture- or recombinant-based vaccines
- an A/Wisconsin/67/2022 (H1N1)pdm09-like virus;
- an A/Massachusetts/18/2022 (H3N2)-like virus; and
- a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
For quadrivalent egg- or cell culture-based or recombinant vaccines for use in the 2024-2025 northern hemisphere influenza season: While the B/Yamagata lineage vaccine component should be excluded as it is no longer warranted, where quadrivalent vaccines are still in use, the B/Yamagata lineage component remains unchanged: Egg-, cell- or recombinant-based Vaccines:
- a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.
Source.
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