US Measles Outbreak Is Largest Since 1991 as Six Deaths Are Reported

Measles has killed six people in the United States this year as the country records its largest outbreak of the virus since 1991, according to figures published on the CDC website on Thursday.

The newly reported total is twice the number of deaths recorded in 2025. More than 5,400 cases have been reported nationwide according to data from the Johns Hopkins University International Vaccine Access Center tracker, while the CDC has reported a national total of 5,182 confirmed cases.

Pennsylvania has been the state most severely affected by the outbreak, confirming six measles-associated deaths this year. On election day, a young child also passed away in New York, and an infant in Wisconsin died several days later.

Pennsylvania officials confirmed six deaths, the Wisconsin department of health services confirmed the infant’s death, and New York recorded its first known measles-related fatality in more than three decades. The CDC did not identify which states accounted for the six deaths included in its official count.

Vaccination Efforts Drove Measles Elimination in the United States

A meeting is underway that will determine whether the United States has lost its measles elimination status. Statistics provided by the Centers for Disease Control and Prevention indicate that prior to the introduction of the initial measles immunization in 1963, annual infections reached an estimated several million alongside hundreds of fatalities.

A successful vaccination campaign drove case numbers to historic lows, and the virus was declared eliminated from the U.S. in 2000. In 1963, the first measles vaccine was licensed and approved using a live, weakened version of the Edmonston-B strain of measles virus, tested on small groups of children ahead of trials involving thousands of children in the U.S. and Nigeria, according to the World Health Organization.

An inactivated vaccine produced by Pfizer also became available in 1963. Data from the CDC shows that while 9 months was the advised vaccination age back in 1963, this guideline shifted to 12 months in 1965 because older children exhibited a superior immune response.

After 1967, the inactivated vaccine was discontinued. Widespread vaccination began to drive down recorded cases, and by 1981 the number of reported measles cases was 80% lower compared to the previous year.

In the late 1980s, measles outbreaks occurred primarily among unvaccinated preschool-aged children and vaccinated school-aged children. Consequently, the American Academy of Pediatrics, the American Academy of Family Physicians, and the CDC’s Advisory Committee on Immunization Practices jointly advised in 1989 that school-age children should be given a second MMR booster.

Measles Cases Rise Across Kentucky Counties

Across 14 counties in Kentucky, more than 200 measles cases have been confirmed, with a majority in unvaccinated people. Carroll, Trimble, Owen, and Lewis counties reported cases. The Ohio Department of Health confirmed 202 cases in 2026 as of last week, more than five times the total of 40 cases confirmed in 2025.

The difference in reported figures followed a change in how the CDC tracks measles fatalities under US health secretary Robert F Kennedy Jr. The agency is now using data from the National Center for Health Statistics to track mortality trends over time, according to a note published to the agency’s website on September 4.

Based on reporting from Reuters, Kennedy had earlier asserted without proof that a pair of fatalities in Pennsylvania might be unrelated to measles, and he urged CDC director Erica Schwartz to exclude those deaths from the official agency count.

“Robert F. Kennedy Jr. does not believe that measles is a big problem and does not want to believe that there are deaths from measles,” Adam Ratner, a paediatric infectious disease specialist, told AFP.

“The burden of these diseases will fall on children, who are not the ones who are making these decisions,” Ratner added.

Measles typically causes fever, respiratory symptoms, and a skin rash, and can lead to complications including pneumonia and inflammation of the brain. Measles is preventable through the measles, mumps and rubella vaccine, which offers approximately 97% protection after two doses.

“Tragic, and that is completely preventable,” Ratner said.

Disclaimer: The information provided in this article is for educational and scientific communication purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider regarding any medical condition, diagnosis, or treatment plan.