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May 28, 2024

Measles elimination in the U.S. is under ‘renewed threat,’ CDC warns

Measles elimination in the U.S. is under ‘renewed threat,’ CDC warns

Measles has spread at a rapid clip this year. From January to March, the U.S. recorded around 30% of the total cases seen since the beginning of 2020. 

From 2020 through 2023, the U.S. recorded an average of five measles cases in the first quarter of each year. Those low numbers were due, in part, to the Covid pandemic, when fewer people were interacting in person. By contrast, this year’s first-quarter tally was 97, according to a report the Centers for Disease Control and Prevention released Thursday.

“The rapid increase in the number of reported measles cases during the first quarter of 2024 represents a renewed threat to elimination,” the authors wrote. 

Measles has been considered eliminated in the U.S. since 2000, meaning the disease is no longer constantly present, though there are still occasional outbreaks.

The country nearly lost that elimination status in 2019, when it recorded more than 1,200 cases — most of which were associated with outbreaks in Orthodox Jewish communities in New York. The high case load this year could put that elimination in jeopardy once again: As of April 4, the U.S. had already recorded seven outbreaks and 113 cases.

The CDC report called for more widespread vaccination coverage. Around 91% of measles cases recorded in the U.S. since January 2020 were among people who were unvaccinated or had an unknown vaccination status, it said.

One dose of the measles, mumps and rubella (MMR) vaccine is 93% effective at preventing measles, and two doses are 97% effective.

This year so far, 83% of recorded cases have been in people who were unvaccinated or whose vaccination status is unknown. Half of the 2024 cases have been in children under age 5. So far, 65 people have been hospitalized.

No one has died of measles in the last four years, according to the CDC report.

Measles vaccination rates dipped in the last few years. Communities should have around 95% vaccination coverage to prevent sustained measles transmission, but 12 states and Washington, D.C., had rates below 90% as of the 2022-23 school year.

The share of U.S. kindergartners who had received two doses of the MMR vaccine fell from 95% in the 2019-20 school year to 93% in the 2022-23 school year. According to the CDC, that leaves around 250,000 kindergarteners susceptible to measles each year.

Vaccination coverage has also declined globally. Around 83% of people worldwide had received one dose of a measles vaccine in 2022, down from 86% in 2019, according to the CDC. Global coverage declined to 81% during the Covid pandemic — the lowest since 2008.

The CDC report encouraged vaccination before international travel, since the majority of measles cases are introduced to the U.S. from other countries. According to the CDC, the number of countries reporting “large or disruptive” measles outbreaks increased 123% from November 2022 to October 2023. 

In the U.S., the largest outbreak this year began at a migrant shelter in Chicago. The city’s measles case total topped 60 this week. Since last month, the Chicago Department of Public Health has distributed more than 13,000 measles vaccines to help contain the spread.

Measles is highly contagious: An infected person can spread it to up to 90% of people close to them if those contacts aren’t immune.

However, the CDC report noted that the “risk for widespread U.S. measles transmission remains low because of high population immunity.”

Aria Bendix

Aria Bendix is the breaking health reporter for NBC News Digital.

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