The FDA’s vaccine advisory committee has unanimously recommended updating the strains included in this fall’s flu vaccines, endorsing a new variant that emerged late in 2025 and quickly became dominant.
On March 12, members of the Vaccine and Related Biological Products Advisory Committee voted to recommend that 2026-2027 influenza vaccines include a new variant known as subclade K. The recommendation will now go to FDA Commissioner Martin Makary, MD, who will make the final decision on the vaccine composition.
Subclade K is a version of the H3N2 influenza virus that emerged in late 2025 and has since become the dominant strain circulating in the Northern Hemisphere. Because the strain appeared after manufacturers had already finalized the vaccine composition, it was not included in this season’s shots. The variant has been linked to earlier and more intense flu outbreaks in several countries, including the U.S., contributing to a surge in admissions and capacity strain at many hospitals this winter.
The FDA panel’s vote aligns with recommendations issued by the World Health Organization in late February. The WHO advised updating all three strains included in Northern Hemisphere vaccines for the 2026-27 flu season, including adding the subclade K variant.
Flu vaccine composition decisions are typically made in February or March each year because manufacturers require several months to produce and distribute the doses ahead of the fall vaccination campaign.
Interim CDC data published March 12 suggests flu vaccines offered more limited protection during the 2025-26 season. Based on data from September through February, vaccination reduced influenza-related outpatient visits among children by 38% to 41% and lowered hospitalization risk by about 41%. Among adults, effectiveness ranged from 22% to 34% against outpatient illness and about 30% against hospitalization.
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