Researchers have mapped uptake of the measles, mumps, and rubella (MMR) vaccine across the United States, identifying large swaths of low uptake, indicating an increased risk of outbreaks at a time of surging measles cases, per a report published yesterday in Nature Health.
Investigators at the Icahn School of Medicine at Mount Sinai and Boston Children’s Hospital used a validated digital participatory surveillance platform to collect and model parental reports of MMR vaccination status among children aged 6 months to 5 years. The team applied small-area methods to produce granular, county-level uptake estimates across the country.
The sample was made up of 22,062 parents in 3,109 counties surveyed from July 2023 to April 2024. Counties were grouped into five risk categories based on predicted coverage: very high risk (less than 60% uptake), high risk (60% to 69%), medium risk (70% to 79%), low risk (80% to 84%) and lowest risk (85% or higher).
“Current surveillance systems rely primarily on telephone surveys with provider verification or school-entry data, methods prone to incompleteness and systematic exclusion of vulnerable populations,” the study authors wrote.
“Our approach complements existing surveillance systems, including recently published county-level reports of two-dose MMR coverage, by better capturing populations who might otherwise be absent from official reporting, including homeschooled and uninsured children,” they added.
Lead author Eric Zhou, PhD, of the Icahn School of Medicine, told CIDRAP News that the intent of the study is not to direct local health departments on what actions to take. “Local leaders have a better understanding of their communities, constraints, and on-the-ground realities,” he said. “Rather, this type of surveillance can complement existing knowledge by offering earlier signals and finer spatial detail—such as ZIP-level variation or cross-county patterns—that may not be apparent from local data alone.”
Overall vaccination rate of 64%
The overall survey-weighted estimate of MMR vaccine uptake of at least one dose was 64.0%, representing about 71.1% of eligible children. For reference, the community immunity threshold is 92% to 94%. Coverage differed substantially by parental characteristics such as age, race, and COVID-19 vaccination status.
The Northeast, Midwest, Northwest, and Pacific coast had high MMR vaccine uptake, and clusters of high coverage were concentrated in the Northeast and Upper Midwest. Low coverage was seen in West Texas, southern New Mexico, northern Arizona, parts of Mississippi, and the rural Southeast.
At the state level, county-aggregated estimates ranged from 61.6% in New Mexico to 79.1% in Massachusetts (median, 71.3%). County-level estimates showed even wider variation, with a median uptake of 71.4% (range, 35.8% to 86.8%). Counties with the lowest uptake were mainly in Georgia, Mississippi, and Texas, with the highest coverage in parts of Indiana, New York, and Oregon.
A comparison of state-level model estimates and provider-verified 36-month single-dose MMR coverage data from the Centers for Disease Control and Prevention (CDC) showed that the model-based estimates were substantially lower than the CDC-reported statistics in two states (New Mexico, 61.6% vs 90.3%; Texas, 62.9% vs 93.7%). These states were also the only ones experiencing substantial measles outbreaks at the time of the analysis.
An examination of county-level patterns in Texas revealed that measles cases were more than twice as likely to occur in areas with both low vaccination coverage and low-coverage neighboring states, suggesting that spatial vulnerability and low vaccination rates among young children may help explain the higher risk of outbreaks, the authors said.
Need for targeted public health interventions
“These granular estimates reveal substantial gaps in coverage, highlighting the critical role of local variation in vaccine-induced immunity in shaping measles vulnerability,” the researchers wrote. “These findings underscore the urgent need for surveillance systems to include more granular and timely data that accurately identify undervaccinated communities, enabling targeted, timely public health interventions.”
Declining MMR coverage, fuelled by multifaceted vaccine hesitancyand pandemic-related disruption, has left national coverage below thresholds required to prevent sustained transmission.
Zhou said, “The value of the work is in expanding the information available to support locally led, context-specific public health decisions, particularly during periods when timely data on young children are otherwise limited or delayed. With this additional information, the goal would be to build outreach programs that speak to the concerns and foster trust between parents and providers, which in turn, hopefully increases our overall MMR vaccine rates.”
So far this year, 171 measles cases have been reported to the CDC, all related to outbreaks that began in 2025. Of those, 145 infections (85%) have been in South Carolina.
Last year, the country logged 2,242 cases, 89% of them linked to 49 outbreaks. In total, 11% of last year’s patients were hospitalized, and three died, two of them children. Roughly 93% of infections in 2025 and 95% this year were among unvaccinated people or those with an unknown vaccination status.
“Declining MMR coverage, fuelled by multifaceted vaccine hesitancyand pandemic-related disruption, has left national coverage below thresholds required to prevent sustained transmission,” the researchers wrote. “Differences in vaccination coverage by geographic, socioeconomic and demographic factors have further contributed to pockets of vulnerability, particularly in communities with lower MMR vaccine rates.”
