Why was the flu vaccine only 25-30% effective for adults this season?

The flu vaccine's lower effectiveness was primarily due to a mismatch between the strains targeted by the vaccine and the dominant H3N2 flu virus, known as subclade K, that spread widely this winter.

What is being done to improve flu vaccine effectiveness for next season?

Scientists are planning next season's vaccines to include protection against the subclade K strain of H3N2, which was the dominant virus this past season, aiming to improve future effectiveness.

How many children have died from the flu this season?

So far this season, at least 101 children have died from the flu, with a significant majority of those cases involving children who were not fully vaccinated.

Home / Health / Flu Vaccine Weak: Only 25% Effective This Season

Flu Vaccine Weak: Only 25% Effective This Season

16 Mar

•

Summary

Flu vaccine offered only 25-30% protection for adults this season.
A dominant H3N2 flu strain mismatch caused lower vaccine effectiveness.
New flu vaccines for next season will target the current dominant strain.

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.