Fall vaccination season is underway, and health officials are urging Americans to get their flu shot by the end of October — with this year’s vaccine reformulated to chase a strain that hammered hospitals last winter.
All U.S. flu vaccines for the 2026-27 season are trivalent, targeting two influenza A viruses and one B virus. Every component was updated from last season, including protection against an H3N2 subclade that spread widely during 2025-26 and earned a ‘super flu’ nickname for the hospitalizations it caused. The Food and Drug Administration recommended the updated composition in March, covering egg-based, cell-based and recombinant products. A new mRNA flu vaccine, approved in August for adults over 50, debuts this fall.
The Centers for Disease Control and Prevention recommends annual flu vaccination for everyone six months and older, with September and October the preferred window for most people who need a single dose — early enough to build protection before circulation peaks, late enough that immunity does not wane before it does. Children who need two doses should start as soon as vaccine is available. For adults 65 and older, medical groups preferentially recommend enhanced options — high-dose, recombinant or adjuvanted vaccines — designed to provoke a stronger immune response.
Officials expect a moderate season nationally, though severity is notoriously hard to predict before transmission takes off. Last year’s season was moderate overall but hit children harder. Vaccination remains available after October for as long as flu viruses circulate, and officials stress that a late shot beats none at all.
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