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Flu Vaccine Fails: New Strain Defeats Shot
13 Mar
Summary
- This season's flu vaccine was only 25-30% effective for adults.
- A new H3N2 flu strain was not well matched to the vaccine.
- 27 million illnesses, 350,000 hospitalizations, and 22,000 deaths occurred.
The recent U.S. flu season concluded with significantly low vaccine effectiveness, marking one of the worst rates in over a decade. Health officials reported that the vaccine was only about 25% to 30% effective in preventing adults from seeking medical attention. For children, the effectiveness was around 40% in preventing doctor's visits or hospitalizations.
A primary factor contributing to this diminished protection was the emergence of a new flu strain, a variant of H3N2 identified as subclade K. This strain proved difficult for the vaccine to target effectively, leading to an intense surge in flu cases during the early winter months. New York City health officials described it as the most severe season in two decades.
Despite the vaccine's performance, health experts emphasize its continued importance in preventing severe illness and death. The Centers for Disease Control and Prevention estimates that as of last week, there have been at least 27 million illnesses, 350,000 hospitalizations, and 22,000 deaths nationwide this season. Efforts are already underway for next winter's vaccine, with recommendations for the 2026-27 season to target subclade K.
