New Flu Strain Weakened This Year’s Vaccine Protection, CDC Says

MONDAY, March 16, 2026 (HealthDay News) — Flu activity in the United States is finally slowing down, but health experts say this year’s flu vaccine didn't offer as much protection as officials hoped.

New data from the U.S. Centers for Disease Control and Prevention (CDC) shows that the vaccine was only about 25% to 30% effective in preventing illness serious enough to send adults to the doctor’s office or hospital.

Among kids, the vaccine reduced the risk of needing medical treatment by about 40%.

While health officials generally consider flu vaccines successful when they are 40% to 60% effective, this season’s protection ranked among the lowest in two decades.