Unvaccinated Drive Worst Single Measles Outbreak Since 2000

The measles outbreak in the Southwest of the United States is ongoing with at least 800 cases recorded in 2025 as of April 17, according to data from the Centers for Disease Control and Prevention (CDC). This is the highest number of cases in a single U.S. outbreak since 2000. These figures reflect confirmed measles cases and so true numbers are likely higher.

CDC data shows that of the 800 cases, 96 percent were unvaccinated or had an unknown vaccination status. Only one percent of cases was among those who had received one dose of the MMR vaccine, which covers measles, mumps and rubella, while two percent of cases reported having had two MMR doses. While it is unlikely someone with two doses (and therefore full coverage) of the MMR vaccine can develop measles, it is still possible at 97 percent efficacy and 93 percent for one dose.

Measles cases have been reported across 25 jurisdictions, with the highest numbers found in Texas (250+) and New Mexico (50-99). So far, there have been three confirmed deaths from measles across the U.S. in 2025 and 85 out of the 800 have been hospitalized with the disease.

The U.S. had managed to eliminate measles from the country in 2000, meaning that it was no longer spreading and new cases were only discovered after people contracted the disease abroad. However, it has continued to be reintroduced from countries where it remains prevalent and declining vaccination rates have enabled outbreaks.

According to the CDC, when more than 95 percent of people in a community are vaccinated, most people are protected through herd immunity. Vaccination coverage among U.S. kindergartners has decreased from 95.2 percent during 2019-2020 to 92.7 percent in 2023-2024, with levels of protection varying across different communities.