Is the 2025-2026 flu shot effective against the H3N2 subclade K strain?

Yes, early research indicates the current flu shot can provide protection against the H3N2 subclade K strain, despite it being a recent mutation.

What is the current level of flu activity in the U.S.?

Flu is surging across most of the U.S., with doctor visits for flu-like symptoms at their highest levels in nearly 30 years.

Why are pediatric flu vaccination rates low?

Pediatric flu vaccination rates are at their lowest recorded levels since 2019, a concerning trend given the severity of the current flu season.

Home / Health / Flu Shot Surprise: Effective Against New Strain

Flu Shot Surprise: Effective Against New Strain

7 Jan

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Summary

Current flu shot shows unexpected effectiveness against a mutated H3N2 strain.
Nearly 1 in 10 outpatient visits were for flu symptoms recently.
Vaccination rates for children are at their lowest in years.

Flu Shot Surprise: Effective Against New Strain

This year's flu shot offers surprising protection against a recently emerged H3N2 subclade K flu strain, according to new research. While the strain mutated too late to be included in the current vaccine, early evidence suggests the vaccine stimulates antibodies that can provide significant protection.

This finding offers a critical positive outlook amidst a severe flu season where flu-like illness has led to the highest number of doctor visits for this time of year in nearly three decades. As of December 27, flu symptoms accounted for nearly 10% of all outpatient visits.

Despite the vaccine's potential, uptake remains a concern, particularly among children, with vaccination rates for those under 18 at their lowest since at least 2019. Experts stress that even an imperfect vaccine offers better protection than none, especially against severe illness.