Nature Medicine, Published online: 20 August 2026; doi:10.1038/s41591-026-04612-2
A nationwide analysis of measles vaccination records from more than 50,000 US schools shows that measles transmission risk crossed the threshold that can lead to epidemics at the school level in the 2–3 years before the 2025–2026 outbreaks, whereas county-level estimates always remained below that threshold.
