Study highlights the fragility of measles elimination in the United States

A new study examined measles vaccination coverage following a large postelimination outbreak, primarily affecting unvaccinated children. Findings from the study will be presented during the Pediatric Academic Societies (PAS) 2026 Meeting, taking place April 24-27 in Boston.

Measles, one of the most contagious vaccine-preventable diseases, requires ≥93 % population immunity to prevent sustained transmission. In 2022–2023, a large postelimination outbreak occurred in central Ohio. Public health interventions-including outbreak notifications, quarantines, and expanded vaccination access-were implemented. However, robust local estimates of measles–mumps–rubella (MMR) vaccination coverage are limited. Prior outbreak reports identified children of Somali-descent as disproportionately affected, underscoring the need to assess subgroup disparities to sustain elimination, strengthen immunization systems, and inform surveillance.

The study found that 20 months after the outbreak, MMR coverage across the entire primary care network (PCN) population remained well below herd immunity levels, with minimal gains. These findings highlight the fragility of measles elimination, showing that even after a postelimination outbreak, system-wide immunity deficits persist and require sustained, equity-focused strategies.

"Our findings show that measles outbreaks reveal, but do not resolve, underlying gaps in population immunity," said Rosemary Martoma, MD, fellow at Boston Children's Hospital and Harvard Medical School and lead author of the study.

Addressing these gaps requires coordinated public health efforts, including vaccination, timely awareness in healthcare settings, early identification of cases, and community-centered outreach."

Rosemary Martoma, Boston Children's Hospital

This work was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) of the National Institutes of Health (NIH) under award number T32HD040128.

Additional information is included in the below research abstract. The PAS Meeting connects thousands of leading pediatric researchers, clinicians and educators worldwide. View the full schedule in the PAS 2026 program guide. For more information about the PAS Meeting, please visit www.pas-meeting.org.