For how we live.
A cluster-randomised trial in nearly 2,000 US nursing homes found fewer confirmed influenza outbreaks with a recombinant vaccine in a moderate flu season, but no difference in a near-flu-free one.
WHO flagged a drifted A(H3N2) subclade K in December; the first 2025-2026 effectiveness data, from 1.4 million US veterans, put overall protection near 22% and protection against hospitalisation near 32%.
Three surveillance networks put 2025/26 effectiveness between 22% and 45% against a drifted H3N2 virus. The figure is a comparison between vaccinated and unvaccinated people who all got tested.
WHO updated all three components for the 2026-2027 northern hemisphere season after subclade K dominated globally, and recommended a new candidate vaccine virus for an H9N2 avian strain.
The 5 December directive tells HHS and the CDC to compare the American childhood schedule with those of other wealthy nations, using a count of diseases as its benchmark.