Flu Vaccine Weak: Only 25% Effective This Season

Flu activity in the United States is decreasing as the winter respiratory virus season nears its end. However, this year's flu vaccine provided lower-than-expected protection, with effectiveness rates around 25% to 30% for adults and about 40% for children.

Experts attribute this reduced protection primarily to a mismatch with the dominant flu strain, an H3N2 virus known as subclade K, which emerged unexpectedly and spread widely. The vaccine used this winter targeted a different version of H3N2.

Despite the vaccine's limitations this season, health experts stress that vaccination still plays a crucial role in mitigating the risk of severe illness. Scientists are actively developing next season's vaccines, with recommendations made to include protection against the subclade K strain to improve future effectiveness.

Flu infections saw a notable spike in late December, with some areas like New York City experiencing their most intense flu season in two decades. This season, there have been at least 101 pediatric flu deaths, with a high percentage of unvaccinated children among the reported cases. Vaccination rates remained similar to the previous year, with about 46.5% of adults and 48% of children receiving the flu shot by late February.