Measles Returns to America.. and the Community Loses the Weapon of "Herd Immunity"

SadaNews - Despite the availability of a safe and effective vaccine for decades, measles is re-emerging as a health threat in the United States, with outbreaks reported in several states in 2025, a phenomenon linked by recent studies to declining vaccination rates and concerning geographical gaps in vaccine coverage.

Scientists issued a warning in a study prepared by researchers from the Icahn School of Medicine at Mount Sinai and Boston Children’s Hospital, published in the journal Nature Health, where they created, for the first time, a detailed map by county of vaccination rates for children under five years old for the measles, mumps, and rubella (MMR) vaccine.

Data indicates that nearly 30% of reported measles cases in 2025 were among children under five, with hospitalization rates in this group reaching 21%, clearly indicating the severity of the disease in young children. Even more concerning is that over 90% of cases were reported among the unvaccinated.

The study shows that national vaccination coverage has dropped below the threshold required to prevent the sustained transmission of the virus, a level defined as "herd immunity." Researchers link this decline to several factors, primarily vaccine hesitancy and the impacts of the COVID-19 pandemic on routine vaccination programs.

Several states reported cases, but the most notable concentrations were in West Texas and South New Mexico. In Texas, the vaccination rate for kindergarten-aged children was about 93.2% during the 2024–2025 school year, a figure below the necessary protective level, coinciding with clear outbreaks of measles.

Researchers say this coincidence is not accidental, but a direct result of having neighboring areas with low vaccination rates.

The study relied on digital data shared by over 22,000 parents with children under five, collected between July 2023 and April 2024. Using advanced statistical models, researchers estimated vaccination rates in 3109 counties across the United States.

Findings revealed that the average coverage was around 64% only, with significant variation between counties; the highest rate was 86.8%, while the lowest dropped to 35.8%. Researchers considered any figure below 60% to represent a very high risk for outbreaks.

The most at-risk areas grouped in West Texas, South New Mexico, parts of Mississippi, and expansive rural areas in the southeastern United States.

Infection Spreads Through "Immunity Gaps"

The study explained that the risk of contracting measles more than doubles in low-vaccination counties if surrounded by other counties facing the same issue, creating what resembles "corridors" for the transmission of infection.

To facilitate the response, researchers launched public interactive maps showing vaccination rates at the county level, aimed at helping health authorities identify the most at-risk areas and direct vaccination campaigns more accurately and fairly.

The study's authors see this data as an early warning tool that can enhance local preparedness for disease outbreaks and reaffirm that measles is not a disease of the past, but an ongoing risk if vaccination gaps continue.