The World Health Organization recommends the Northern Hemisphere's 2024-25 flu vaccines be trivalent.
On Feb. 23, the WHO told national vaccine regulatory agencies and pharmaceutical companies its recommendations for the viral composition of next season's influenza vaccines.
A trivalent vaccine protects against three strains of the flu, including two influenza A strains and one influenza B strain. Last year, the WHO recommended quadrivalent shots.
For egg-based vaccines — which the CDC recently OK'd for people with egg allergies — the WHO suggests they target 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 are recommended to contain 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.
Quadrivalent vaccines for the 2024-25 Northern Hemisphere flu season are encouraged to also include a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.