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Measles infections in the United States have surged past 4,000 cases so far this year, with confirmed outbreaks in 45 states and Washington, D.C., according to the latest Centers for Disease Control and Prevention (CDC) data. The CDC’s update, released Friday (October 9), marks the highest annual total in decades and raises concerns about the country’s declining vaccination rates and the risk of losing the nation’s measles elimination status.
Most of the 4,080 reported cases are concentrated in states experiencing ongoing outbreaks, including South Carolina, Arizona, California, Florida, and several others. According to the CDC, South Carolina is facing the largest outbreak seen in recent memory, with more than 600 cases. The CDC also reports that 18 of this year’s cases have been among international visitors to the United States.
The majority of those infected are unvaccinated or have unknown vaccination status. As noted by Dr. Demetre Daskalakis, former head of the CDC’s division tracking measles and other diseases, "Because it's such an infectious virus, whenever you see measles outbreaks, it in effect, highlights areas of the country or communities in which vaccination rates are low," as reported by Good Morning America.
CDC data shows the rate of kindergartners vaccinated with the measles, mumps, and rubella (MMR) vaccine has dropped from 95% in 2019 to below 93% for 2025. Herd immunity for measles is generally reached when 95% of a population is vaccinated. The CDC has warned that declining vaccination coverage leaves approximately 300,000 kindergarteners unprotected, allowing outbreaks to spread more easily.
Children and adolescents make up a large portion of the current infections, and about 13% of measles patients this year have required hospitalization, most of them under age 19. The CDC notes that 96% of cases are among people who are unvaccinated or whose vaccination status is unknown.
Health officials continue to urge parents and communities to ensure children receive both recommended doses of the MMR vaccine, which is 97% effective at preventing measles. Public health leaders warn that if widespread transmission continues for 12 months, the United States could lose its measles elimination status, which was first achieved in 2000.
Officials recommend increasing vaccination rates as the most effective strategy to curb the outbreak and protect vulnerable populations. The CDC is closely monitoring the situation as the country heads into the winter months, when respiratory virus activity typically increases.