Each spring in the Northern Hemisphere scientists get together and examine global surveillance data (from both hemispheres) and decide what strains should be included in the upcoming flu season’s vaccine.
It’s important to get it right because how effective the vaccine ends up being depends on whether it correctly guesses what antigens to target. FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) met back in March to select the strains to focus on for the 2023-2024 U.S. influenza season.
The committee recommended that the vaccines for the U.S. 2023-2024 influenza season have the following antigens for the egg-based vaccines. The strain below in bold is the one that has been updated from last year’s shot:
- A/Victoria/4897/2022 (H1N1)pdm09-like virus;
- A/Darwin/9/2021 (H3N2)-like virus;
- B/Austria/1359417/2021-like virus (B/Victoria lineage);
- B/Phuket/3073/2013-like virus (B/Yamagata lineage).
For trivalent influenza vaccines for use in the U.S. for the 2023-2024 influenza season, depending on the manufacturing method of the vaccine, the committee recommended A(H1N1)pdm09, A(H3N2) and B/Austria/1359417/2021-like virus (B/Victoria lineage).
How well flu vaccine works can depend in part on the match between the vaccine viruses and circulating viruses. Preliminary estimates show that last season, people who were vaccinated against flu were about 40% to 70% less likely to be hospitalized because of flu illness or related complications.
