The measles virus, once eliminated in the United States, is back in the spotlight after Texas reported more than 750 cases this year—over half of them in Gaines County alone. The resurgence has been tied to waning measles, mumps, rubella (MMR) vaccination coverage and illustrates the fragility of herd immunity in the face of vaccine hesitancy and disruptions to routine immunization programs.
A new study published in JAMA Health Forum on September 19, 2025, led by researchers at the University of Texas Health Science Center, modeled potential outbreak trajectories across Texas counties. Using epidemiological data from the Gaines County outbreak earlier this year, the team tested how modest changes in vaccination rates could alter epidemic outcomes statewide.
Declining Immunity, Rising Risks
Statewide MMR vaccination coverage among kindergarteners has dropped from 98.5% in 2013–2014 to 94.3% in 2024–2025. The decline was steeper in Gaines County, where rates fell from 92.6% to 82.0% over the same period. These gaps created fertile ground for the January 2025 importation of measles into Gaines County, which triggered extensive local transmission.
What makes measles particularly dangerous is its extreme contagiousness. It is one of the most infectious viruses known, with a single case capable of spreading to 12–18 susceptible people. Unlike many respiratory pathogens, measles can linger in the air for hours after an infected person has left a room. To keep outbreaks at bay, at least 95% of the population must be protected through vaccination—a threshold higher than for nearly any other vaccine-preventable disease.
Modeling the Scenarios
Researchers simulated three scenarios across Texas counties:
- Baseline (current reported vaccination rates)
- 5% reduction in vaccination coverage
- 5% increase in vaccination coverage
Under baseline conditions, multiple counties—including Gaines, Walker, Brazos, Erath, Kent, and Sterling—were projected to experience outbreaks exceeding 12 cases per 1,000 population. When vaccination coverage was modeled at 5% lower than current levels, projected outbreak sizes increased substantially, with some counties facing more than 20 cases and four hospitalizations per 1,000 residents.
Conversely, with a modest 5% boost in coverage, no county was projected to exceed 15 reported cases or three hospitalizations per 1,000 people.
Implications for Public Health Strategy
The findings underscore the disproportionate benefits of even incremental gains in vaccine uptake. Raising coverage by just a few percentage points could prevent hundreds of cases and reduce strain on hospitals.
While the modeling assumed county-level independence and did not account for inter-county spread, it offers a valuable framework for preparedness. Public health agencies can adapt this approach in other settings with robust vaccination and demographic data.
Beyond Texas: Broader Lessons
With U.S. vaccination rates trending downward in several states, the Texas experience serves as a warning. The study highlights how localized lapses in coverage can ignite widespread outbreaks, especially when combined with international importations.
Looking Forward
Texas’ 2025 measles crisis shows how quickly progress can unravel when vaccination coverage slips. For policymakers, clinicians, and community leaders, the challenge is twofold: restoring public confidence in vaccines and reinforcing routine immunization systems disrupted by the COVID-19 pandemic and other pressures.
If the projections hold, achieving even modest increases in MMR uptake could spell the difference between contained clusters and statewide epidemics.
Bi K, Nguyen T, Peng B, et al. Modeling the Impact of MMR Vaccination Strategies on Measles Outbreaks in Texas. JAMA Health Forum. 19 September 2025.