What you need to know
- The U.S. eliminated measles in 2000. The designation means that, while measles cases still occur, the disease does not spread continuously as it once did.
- In January 2025, measles cases in West Texas surged, starting the largest outbreak in decades. One year later, the United States is at risk of losing its measles elimination status.
- International health officials will meet this spring to determine if the outbreaks still affecting several states are linked to the original outbreak in Texas.
2025 was the United States’s worst year for measles since 1991, with over 2,200 cases reported. Now, global health experts are trying to determine if the record-setting year will cost the U.S. its measles elimination status.
The status hinges on one crucial question: Are the ongoing outbreaks in South Carolina and other states linked to the West Texas outbreak that began over a year ago?
If so, that means the chain of transmission has continued uninterrupted for over 12 months, and the U.S. can no longer be considered “measles-free.”
“Although measles has been circulating in the U.S. throughout 2025, it isn’t clear yet whether these outbreaks are linked,” said Dr. Sara Oliver, a scientist at the Centers for Disease Control and Prevention, according to reporting by the New York Times.
In April, the Pan American Health Organization will meet to review the measles elimination status of the U.S. and Mexico. The organization confirmed the loss of Canada’s measles-free status in November 2025.
What is disease elimination?
A disease is “eliminated” when humans stop its spread in a country or region. Outbreaks may occur after elimination, but the disease is no longer considered endemic (continuously circulating in an area). Elimination differs from eradication, which only occurs when a disease is eliminated globally.
Although only one human disease (smallpox) has been successfully eradicated, several have been eliminated thanks to vaccines.
In 2000, the U.S. declared measles eliminated more than two decades after the CDC launched a successful mass vaccination campaign. But the country can lose its elimination status if measles outbreaks continue for a year or more.
Why are measles cases rising?
Since the early 1990s, high vaccination rates have kept annual U.S. measles cases relatively low, with some notable exceptions. Until this year, a 2019 outbreak originating in New York City was the worst to occur since measles was eliminated in the U.S.
The 2019 outbreak infected over 1,200 people, resulting from low vaccination rates and a misguided reliance on “natural” immunity.
In Gaines County, Texas, the epicenter of the original 2025 outbreak, one in five kindergartners had not received the measles, mumps, and rubella (MMR) vaccine. That’s well below the 95 percent vaccination rate needed to maintain herd immunity, which occurs when enough of a population has immunity to prevent a disease from easily spreading.
Additionally, childhood vaccinations declined during the COVID-19 pandemic and have yet to recover as anti-vaccine beliefs drive vaccine hesitancy. Recent polls show declining trust in vaccines and decreased support for school vaccine requirements in the U.S.
How might the U.S lose its elimination status, and how can we prevent it?
When measles cases spiked in 2025, a JAMA study found that at current immunization levels, the U.S. would be well on its way to losing measles elimination status.
“With measles, we found that we’re already on the precipice of disaster,” said Mathew Kiang, the study’s lead author and assistant professor of epidemiology at Stanford University, in an April 2025 interview.
“If vaccination rates remain the same, the model predicts that measles may become endemic within about 20 years.”
The trend is not limited to the U.S. A global rise in measles cases and a decline in childhood immunizations signal a significant public health setback. Diseases that were on the decline for decades may reemerge, leading to millions of unnecessary illnesses and deaths.
“Measles is a canary in the coal mine,” wrote epidemiologist Katelyn Jetelina and emergency medicine physician Dr. Kristen Panthagani. “When measles reappears in a country like the U.S., it signals that something has gone seriously wrong.”
They added that “this is not just a failure to move forward—it’s the unraveling of decades of progress, representing one of the greatest public health achievements of our era.”
The best tool to prevent a measles comeback—the MMR vaccine—is readily available. Only 4 percent of measles cases in 2025 were in fully vaccinated people.
Two doses of the MMR vaccine are 97 percent effective against measles and provide lifelong protection.
“Increasing vaccination levels by just 5% brings the number of measles cases down, safely away from returning to endemic levels,” said Dr. Nathan Lo, assistant professor of infectious diseases at Stanford and the senior author of the JAMA study.
Vaccination is the safest and most effective way to protect children and prevent the spread of measles. For more information about measles and the MMR vaccine, talk to your health care provider.