The World Health Organization (WHO) today announced the flu vaccine strain recommendations from its advisory group for the Northern Hemisphere 2024-25 flu season, which are the same as the group recommended for the Southern Hemisphere's 2024 season.
As for its recommendation for the Southern Hemisphere seasonal flu vaccines in September, the WHO experts recommends that companies switch back to trivalent (three-strain) vaccines and leave out the influenza B Yamagata lineage component.
Yamagata B lineage not detected since 2020
In accompanying background information, the WHO said no naturally occurring influenza B Yamagata lineage viruses have been confirmed since March 2020 and that the vaccine strain isn't needed anymore.
The recommendations for egg-based and cell-based vaccine strains vary, and the latest picks for both versions of the Northern Hemisphere vaccines are the same those recommended for the Southern Hemisphere.
For countries that still use quadrivalent (four-strain) versions of the vaccine containing a second B strain, the WHO recommends a strain similar to the Yamagata Phuket/3073/2013 lineage virus, the same as other recent picks.
Advisers pick 2 new pandemic preparedness vaccine viruses
During their twice-a-year meetings to recommend strains to include in seasonal flu vaccines, the WHO's advisory group also examines the latest developments with zoonotic flu strains to see if any new viruses are different enough from earlier strains to warrant new candidate vaccine strains for pandemic preparedness.
At its meeting, the group proposed two new candidate strains, both targeting recent variant H1N1 viruses. One is antigenically similar to A/Catalonia/NSAV198289092/2023, and the other is similar to A/England/234600203/2023.