The 2025 measles outbreak in Texas

BACKGROUND: In 2025, Texas experienced its largest measles outbreak in decades, reporting 762 cases by mid-August. Measles is a highly contagious but vaccine-preventable infection transmitted mainly among unvaccinated individuals and capable of causing severe outcomes. METHODS: We investigate counterfactual measles control scenarios based on daycare and school closures and reactive vaccination of infants and children, including mixed interventions. We analyze the 2025 Texas outbreak using an age-structured multi-stage SEIR model formulated as a system of ordinary differential equations. The model is fit to case data using Bayesian inference to estimate the effective reproduction number and generate posterior predictive trajectories under alternative closure and vaccination scenarios. RESULTS: The effective reproduction number [Formula: see text] was estimated to have a median of [Formula: see text] with a 95% high density interval (HDI) of 2.1-5.4. Posterior predictive trajectories have medians that closely match the observed data in different age groups. A combined vaccination campaign and short-term closures could reduce the cases by up to 21%. The combined daycare and school closure produced the greatest marginal benefit during the first 7 weeks, after which the additional benefit declined rapidly, which shows diminishing returns. Reactive vaccination campaigns also exhibited diminishing marginal returns, with the number of additional averted cases decreasing nonlinearly with each [Formula: see text] increase in vaccination rate, yielding small gains at higher vaccination levels. CONCLUSIONS: The measles outbreak is probably due to decreased immunity levels in the affected counties. Implementing extended daycare and school closures, supplemented with a swift, reactive vaccination campaign, can be highly effective in containing the local measles outbreak.