CDC Reports Decreased Effectiveness of 2024 Flu Vaccine in Southern Hemisphere

The flu vaccine reduced hospitalization risk by 35% but showed lower efficacy compared to previous years, raising concerns for the Northern Hemisphere's upcoming season.

The 2024 flu vaccine was 34.5% effective against hospitalization in the Southern Hemisphere, a decrease from last year's 51.9%.
The lower effectiveness may be due to a shift in dominant flu strains, with H3N2 more prevalent than H1N1 this year.
U.S. health officials use Southern Hemisphere data to anticipate flu trends, though exact outcomes can vary.
Flu vaccine uptake was notably low, with only 21.3% coverage in the studied South American countries.
Despite reduced effectiveness, vaccination remains a key strategy to prevent serious flu complications.