In a significant change for the upcoming flu season, America’s flu shots for 2024-2025 will only protect against three types of flu virus instead of the typical four. The Yamagata lineage of the influenza B family tree, which was a common flu virus in the past, has not been seen since March 2020. A panel of FDA advisers has recommended removing Yamagata viruses from the flu shot formulation for next year.

This decision is expected to have several positive impacts. By eliminating the need to include the Yamagata virus in flu vaccines, production capacity for flu vaccines could increase. Additionally, potential risks associated with growing the Yamagata virus in a lab will be eliminated. Health experts believe that vaccinating against an extinct virus like Yamagata is unnecessary.

Manufacturers are already preparing to switch to trivalent vaccines for the U.S. starting next flu season. The FDA has confirmed that all U.S. flu shot manufacturers have submitted the required regulatory paperwork to make trivalent vaccines. However, scientists will continue to monitor for Yamagata viruses and other flu strains that infect people.

Overall, the decision to remove the Yamagata virus from the flu shot formulation for the 2024-2025 season is seen as a positive step to improve the production and safety of flu vaccines. This change aligns with the goal of ensuring that flu shots are effective at protecting against the most prevalent strains of the flu each year. The public can expect to see trivalent vaccines available for the upcoming flu season.