Measles outbreaks threaten disease's elimination status

According to CDC, measles cases recorded between January and March of this year amounted to nearly 30% of the total number of measles cases recorded since the start of 2020.

Between 2020 and 2023, the United States recorded an average of five measles cases in the first quarter of each year. So far this year, the United States has recorded 97 measles cases in the first quarter, and as of April 4, the United States has seen seven measles outbreaks and 113 total cases.

"The rapid increase in the number of reported measles cases during the first quarter of 2024 represents a renewed threat to elimination," the report said.

However, CDC did note that "risk for widespread U.S. measles transmission remains low because of high population immunity."

Since 2000, measles has been considered eliminated in the United States, meaning it is no longer constantly present despite occasional outbreaks. However, the United States almost lost its elimination status in 2019, when more than 1,200 cases were recorded.

General symptoms of measles can include fever, cough, runny nose, watery eyes, and a rash of red spots. Around one in five unvaccinated people in the United States who get measles will be hospitalized, according to CDC, and around one in every 20 children with measles will develop pneumonia, while others could develop a dangerous brain swelling called encephalitis.

Up to three in 1,000 children who get measles could die from respiratory and neurologic complications, however CDC noted that no one has died from measles in the past four years.

CDC calls for widespread vaccinations

In response to measles outbreaks nationwide, CDC called for more widespread vaccination coverage. Roughly 91% of measles cases in the United States since January 2020 were among those who were either unvaccinated or had an unknown vaccination status, CDC said. So far this year, 83% of recorded measles cases have been among either the unvaccinated or those with an unknown vaccination status.

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

Allison Bartlett, a professor of pediatrics at the University of Chicago's medical school, said the uptick in measles cases is a "very serious wake-up call."

"This is a very, very preventable illness by vaccination. But it requires very high levels of individuals being vaccinated," Bartlett said.

Measles vaccination rates have dropped over the past few years. According to CDC, communities should have around 95% vaccination coverage to prevent sustained measles transmission, however 12 states and Washington, D.C. had vaccination rates below 90% as of the 2022-23 school year.

In addition, the percentage of kindergarteners in the United States who received two doses of the MMR vaccine dropped from 95% in the 2019-2020 school year to 93% in the 2022-2023 school year. That means roughly 250,000 kindergartners are susceptible to measles each year, according to CDC.

"The overwhelming scientific evidence shows that vaccines remain among the most effective and safest intervention to both prevent individual illness and protect the health of the public," said Jesse Ehrenfeld, president of the American Medical Association.

In its report, CDC encouraged vaccination before any international travel, as the majority of measles cases are introduced to the United States from other countries. According to CDC, the number of countries reporting "large or disruptive" measles outbreaks increased 123% from November 2022 to October 2023.

"Maintaining measles elimination status is an important public health benchmark," said Marcus Plescia, CMO of the Association of State and Territorial Health Officials. "Public health jurisdictions are reaching out to communities and populations with low vaccination rates and we feel this approach will be effective. However, the increase in misinformation about measles vaccination undermines these efforts and could ultimately endanger our elimination status." (Bendix, NBC News, 4/11; McPhillips, CNN, 4/11; Kim, NPR, 4/12)

Writing for The Atlantic, Sarah Zhang analyzes how past and present vaccination campaigns in the United States have attempted to boost child vaccination rates — and why vaccine uptake among children has never been "immediately universal."