Global Measles Cases Jumped 20%. Here's How That Could Affect You

The number of measles cases increased by 20% around the world in 2023 compared to 2022, according to a report by the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC).

A statement about the report attributed the uptick to “inadequate immunization coverage.” More than 22 million children did not receive a first dose of the two-dose measles vaccine last year.

“Measles vaccine has saved more lives than any other vaccine in the past 50 years,” Tedros Adhanom Ghebreyesus, PhD, WHO Director-General, said in the statement. “To save even more lives and stop this deadly virus from harming the most vulnerable, we must invest in immunization for every person, no matter where they live.”

Measles was declared eliminated in the United States in 2000, but outbreaks have continued to crop up. So far this year, the U.S. has seen 277 measles cases, most of which were associated with 16 outbreaks.Experts warn that declining vaccination rates may leave some U.S. communities vulnerable to this highly contagious and potentially fatal disease.

“The majority of our outbreaks begin after somebody travels internationally, gets measles, and then brings it back to the United States,” said Lori Handy, MD, MSCE, associate director of the Vaccine Education Center at Children’s Hospital of Philadelphia and an attending physician in the Division of Infectious Diseases at the hospital.

“This is a disease where infections that are global quickly become local,” Handy added.

Why Measles Outbreaks Abroad Matter in the U.S.

Measles is one of the most contagious human diseases known, according to the CDC. In communities where fewer than 95% are vaccinated, one person with measles can infect a dozen others.

Globally, about 83% of children received a first dose of the two-dose vaccine last year, and 74% received a second shot, the CDC/WHO report said. According to the report, 57 countries experienced “large or disruptive” measles outbreaks last year.

In 2023, about 107,500 people died of measles, with most deaths occurring in children younger than 5 years old. This represents a slight decline in deaths compared to previous years. The CDC/WHO statement said that's likely because the uptick in cases is in areas where children with measles have access to better nutrition and health services and are thus less likely to die of the disease.

Still, people who survive measles are at risk for serious and sometimes life-long health issues, such as blindness, pneumonia, and brain swelling.

The WHO reverified Brazil as measles-free this year, making the Americas region free of endemic measles. While the U.S. and other countries in the region no longer see consistent transmission of measles, declining vaccination rates leave communities vulnerable to outbreaks.

“If somebody travels abroad and they’re unvaccinated, they can bring measles back into the United States. If they then enter a community that has low vaccination rates, essentially everybody who is unvaccinated in that community is likely to get measles. It’s just that contagious,” Handy said.

Routine childhood vaccination coverage has declined steadily in the U.S. over the past three years. In the 2023–2024 school year, vaccination rates among U.S. kindergartners dropped to 92.7% for measles, mumps, and rubella (MMR)—below the 95% coverage required to prevent outbreaks.

In certain communities, coverage is even lower. In 14 states, fewer than 90% of kindergarteners are vaccinated against MMR.

During the COVID-19 pandemic, many children couldn’t access routine health care, contributing to missed vaccinations. Meanwhile, vaccine hesitancy and misinformation proliferated. Several states have also relaxed their non-medical exemption standards, making it easier for families to legally send their kids to school without vaccinations.

A now-retracted case series study published in 1998 linked the MMR vaccine to autism in a small group of children. The conclusions have been disproven many times, but misinformation and skepticism about the vaccine persist.

What To Know About Measles

Measles is a respiratory virus that spreads through coughing, sneezing, or by touching surfaces contaminated by someone with measles.

The initial symptoms commonly resemble the common cold—cough, runny nose, fever, and red or watery eyes. A full-body rash typically appears three to five days later.

About one in five unvaccinated people in the U.S. with measles will be hospitalized. In rare cases, especially in children younger than 5, serious infections can lead to death.

The CDC recommends that children get two doses of MMR vaccine, starting with the first dose at 12 to 15 months old and the second dose at 4 to 6 years old.

Handy said it’s important that children get vaccinated on time to avoid the potentially serious outcomes of being infected at a young age. Health providers should be particularly aware of the early symptoms of measles so they don’t misdiagnose a case as a different respiratory illness.

“In this era where we have a significant burden of global measles and individuals who are traveling frequently, we really need to have a high index of suspicion. You really need to immediately test that child and isolate them and work with public health officials, because any delay in diagnosis leads to spread within a community,” Handy said.

Adults who do not have evidence of immunity should get at least one dose of MMR vaccine, the CDC says. Adults without evidence of immunity who are in certain high-risk settings, like students at post-high school educational institutions and international travelers, need two doses of the MMR vaccine, separated by at least 28 days.