How many measles cases have been reported in the U.S. in 2025?

As of December 10, the CDC has reported 1,912 measles cases across 47 outbreaks in the U.S. in 2025.

Why is the measles outbreak worsening in the U.S.?

The outbreak is worsening due to a significant drop in vaccination rates and the rise of vaccine exemptions based on personal or religious beliefs.

What is the effectiveness of the MMR vaccine?

The MMR vaccine is approximately 97% effective after two doses and has been instrumental in controlling measles since its introduction.

Which U.S. state is most affected by the 2025 measles outbreak?

South Carolina is currently one of the hardest-hit states, with over 111 confirmed cases and hundreds in quarantine.

Healthcare

Measles Outbreaks Surge as U.S. Nears a Disease Tipping Point

— South Carolina is at the heart of an accelerating outbreak, pushing the U.S. closer to losing its measles elimination status after 25 years.

By Emily Wilson Published: December 12, 2025 Updated: December 12, 2025 28400

Healthcare worker administering MMR vaccine to a child amid U.S. measles outbreak

More than 1,900 Americans had fallen ill from measles in 2025, mostly children. The outbreak has been escalating and is on the verge of erasing the nation’s measles elimination status early next year.

South Carolina is at the heart of what health officials have defined as an “accelerating” outbreak of measles. Hundreds are in quarantine, and more than 111 people have become sick; of those, 105 were unvaccinated. This wave of cases represents one in a series of outbreaks across the country this year, each bringing the United States closer to losing its measles elimination status for the first time in over 25 years.

As of Dec. 10, the C.D.C. had reported 1,912 cases of measles across 47 outbreaks in 2025. By contrast, there were just 16 outbreaks and 285 cases reported in 2024. So far, at least two children have died in the current outbreaks.

These disturbing trends are exacerbated by a dramatic reduction in vaccination rates across communities. The measles vaccine, known as MMR (measles, mumps and rubella), is approximately 97 percent effective after two doses. The U.S. eliminated measles in 2000, due to high vaccination rates that prevented the virus from spreading.

While every state mandates children to be vaccinated against MMR to go to public school, many allow exemptions based on religious or personal beliefs. “Our best-case scenario assumes that the proportion of children who remain unvaccinated in future years will be similar to what we have observed,” South Carolina’s state epidemiologist, Linda Bell, said at a news conference Friday. The World Health Organization recommends vaccination rates of roughly 95 percent to preserve herd immunity and squash outbreaks.

Notable people like Secretary of Health and Human Services Robert F. Kennedy Jr. and former President Donald Trump have complained about the MMR vaccine, arguing that it should be given in separate shots or falsely claiming that it causes autism, a belief for which major scientific studies have since disproved.