Hamilton County Public Health is urging families to check their measles vaccination records as Ohio battles its third outbreak of 2026 and the nation posts case numbers not seen in more than three decades.

The county health department published an advisory on Sept. 8 warning that measles outbreaks are growing more frequent in Ohio and surrounding states. No confirmed cases have been reported in Hamilton County, but the department said it is actively monitoring for local spread. The advisory covers all Hamilton County residents, including families in Indian Hill, Madeira, Mariemont, Terrace Park and Sycamore Township.

The CDC reported 3,134 confirmed U.S. measles cases as of Sept. 3, the highest total since 1991. Ohio is among 47 jurisdictions reporting cases.

Ohio alone has recorded 122 cases this year across 12 counties, according to WVXU, with clusters of 32 in Geauga County and 27 in Ashtabula County. The state logged 45 cases in all of 2025 and just seven in 2024, according to the Ohio Department of Health.

Ohio's three separate 2026 outbreaks began in Cuyahoga County in January, spread to Franklin County in February and continued growing in northeast Ohio through the summer, the Akron Beacon Journal reported. Confirmed cases range in age from 15 months to 20 years old.

Health officials point to declining vaccination rates. Nationally, MMR (measles, mumps and rubella) vaccine coverage among kindergartners dropped from 95.2% in the 2019–2020 school year to 92.4% in 2025–2026, leaving roughly 280,000 children at risk, according to the CDC. In Ohio, 85.4% of approximately 123,700 kindergartners completed their vaccines in 2025–2026, down from 89.9% in 2019–2020, Cleveland.com reported. Non-medical vaccine exemptions among Ohio kindergartners more than doubled in that span, rising from 2.6% to 5.4%.

Among all 2026 U.S. measles patients, 93% were unvaccinated or had unknown vaccination status, according to the Center for Infectious Disease Research and Policy at the University of Minnesota, citing CDC data.

Dr. Bruce Vanderhoff, director of the Ohio Department of Health, said at an Aug. 6 news conference, as reported by Cleveland.com, that "declining vaccination rates threaten to put cracks in the armor that vaccines have given us against deadly diseases."

The two-dose MMR vaccine series is 97% effective at preventing measles. One dose is 93% effective. Hamilton County Public Health noted that a person with measles can infect up to 90% of unvaccinated people they encounter, and the virus can linger in the air for up to two hours after an infected person leaves a room.

About 30% of measles cases lead to at least one complication, according to the health department's fact sheet. As many as one in 20 children with measles develops pneumonia. Symptoms typically appear seven to 14 days after exposure and include fever, cough, runny nose, pink eye and a blotchy red rash.

Ohio law requires students in kindergarten through 12th grade to be vaccinated against 10 diseases, including measles. That requirement was not changed by a federal executive order on childhood vaccines issued in August 2026, according to the Ohio Department of Health.

Residents unsure of their vaccination status can call Hamilton County Public Health at (513) 946-7800 or submit an immunization records request online. Measles vaccinations are typically covered by most health insurance plans, according to the department. Healthcare providers who suspect a case should report it immediately at (513) 946-7874.