Jan. 30, 2024 – It may be reassuring to think that serious measles outbreaks are a problem we conquered in the past or something that only affects people over there – like in Europe, which last year reported 42,200 cases. But complacency here in the United States could come at a price, experts said. 

While measles was considered officially wiped out here in 2000, sporadic, clustered outbreaks continue to pop up. Most notably, measles hit New York City in 2019, central Ohio just 2 years ago, and Philadelphia starting this past December. 

In early January, public health experts warned travelers who passed through two Washington, DC-area airports that they may have been exposed. That highlights just how easy it is for an infected person to pass measles along to other, unvaccinated people. 

The recent number of cases in the U.S. prompted the CDC to issue a nationwide measles alert last week.

COVID Lowered Measles Vaccinations

Measles is an “immense concern,” said Gregory A. Poland, MD, founder and director of the Mayo Clinic Vaccine Research Group in Rochester, MN, and editor-in-chief of the journal Vaccine. He described measles as the “canary in the coal mine” for vaccine-preventable disease. 

Measles is so contagious, he added, that a person coming to an emergency room 12 hours after someone else was there with measles could contract the infection (if not immunized). 

“If SARS-CoV-2 were that transmissible, we’d have millions of more deaths in the U.S. by now,” Poland said.

And speaking of COVID-19, the pandemic led to considerable delays in measles vaccinations. 

“WHO [World Health Organization] data showed that in the year up to November 2022, almost 40 million children worldwide had missed a measles vaccine dose. A historical high of 25 million children skipped their first dosage, and another 14.7 million missed their second,” according to a March 2023 report in the Annals of Medicine and Surgery (London). 

COVID delayed vaccinations in the United States, too. CDC data updated Jan. 12 shows that more than 61 million doses of the MMR vaccine, which contains the measles vaccine, were delayed or missed entirely from 2020 to 2022 due to COVID. “This increases the risk of bigger outbreaks around the world, including the United States,” the agency noted.

At least 8,500 schools nationwide are at risk of a measles outbreak, according to a CBS News investigation that looked at vaccination rates at public and private schools in 19 states. In these instances, the vaccination rate for kindergartners falls below the 95% the CDC says is necessary to achieve herd immunity and protect entire communities.

“Even though we give infants two doses, which can be up to 97% effective, there are still people who remain vulnerable,” said Adam Ratner, MD, director of the Division of Pediatric Infectious Diseases at Hassenfeld Children’s Hospital at NYU Langone in New York City, and a member of the American Academy of Pediatrics Committee on Infectious Diseases. “The measles vaccine is amazing.” Two doses in childhood generally last a lifetime, it doesn’t need updating, and it’s been pretty much the same formula since the 1960s. 

Ways to get more people to take the measles and other vaccines is “really about understanding and trying to engage with different communities about what their concerns are, making vaccination easy, and educating the public,” said Krutika Kuppalli, MD, vice chair of the Infectious Diseases Society of America’s Global Health Committee.

“Measles is called the inequity virus for good reason. It is the disease that will find and attack those who aren’t protected,” Kate O’Brien, director of the World Health Organization’s Department of Immunization, Vaccines and Biologicals, said in a November 2023 WHO news release. “Children everywhere have the right to be protected by the lifesaving measles vaccine, no matter where they live.” 

“The increase in measles outbreaks and deaths is staggering, but unfortunately, not unexpected given the declining vaccination rates we’ve seen in the past few years,” John Vertefeuille, director of CDC’s Global Immunization Division, said in the same release. “Measles cases anywhere pose a risk to all countries and communities where people are under-vaccinated. 

“Urgent, targeted efforts are critical to prevent measles disease and deaths,” Vertefeuille added.

According to a joint CDC-WHO report, there were more than 136,200 global measles deaths in 2022. You have to go back to 2015 to find a measles-related death in the United States

Another challenge with controlling measles outbreaks is the incubation period. Typically, people can have measles for 10 to 14 days before they realize it.

Expert Perspective

Throughout the COVID-19 pandemic, what happened in Europe foretold what we could expect here stateside. Is the same true for measles? We asked experts just how concerned we should be, and what, if anything, about measles keeps them awake at night.

“I’m concerned. It is the most contagious virus we know of,” said William Schaffner, MD, an infectious disease specialist at Vanderbilt University Medical Center in Nashville. “It is the number one, Olympic gold virus in terms of transmission.”

After eliminating measles from the Western Hemisphere, “we got lax,” said Schaffner, who is also a professor of preventive medicine and infectious diseases at Vanderbilt University School of Medicine. “We are now two to three generations from when measles was common in the U.S. A lot of people know the name,” he said, but have never seen measles in their lifetime, including younger doctors. 

Back in the 1950s and early 1960s, so many children got measles that “it was familiar to parents, pediatricians, and everyone else,” Ratner said. “It’s a different story now. “We had a big outbreak in New York right before the pandemic, and for a lot of people I work with, it was their first clinical exposure to measles.” 

Measles, polio, and diphtheria “are things we don’t see as much. It’s really important to remind people how serious they can be,” said Kuppalli. “We should inform people, not in a fearmongering way but in an educational way.”

“People do not have to panic, but every time there is a [measles] case in the U.S. or elsewhere, it is a warning sign,” Ratner added. “People should vaccinate their kids.” 

It’s not just measles either. Globally, there is a resurgence in other vaccine-preventable diseases, like diphtheria and pertussis. 

“This is not just a problem in the U.S. It’s a problem around the world,” added Kuppalli, who is also a medical officer for COVID-19 health operations in the Department of Epidemic and Pandemic Preparedness and Prevention in the Health Emergencies Program at the World Health Organization.

Two other things are adding to the resurgence in these diseases along with the COVID-related vaccination delays. 

“There has also been a rise in vaccine hesitancy because of misinformation and disinformation related to COVID vaccines – and that affects the uptake of other vaccines,” Kuppalli said. “During COVID, people were socially distant. Now, people are traveling more than ever and mixing again.

A Growing Global Threat

Measles cases are not just happening around the world, they are happening more often. The virus is a growing threat, especially to young children, in 37 countries around the world, according to 2022 numbers from the World Health Organization and the CDC. Those case numbers are up 18%, compared to 2021. 

Deaths from measles were also up 43% globally from 2021 to 2022, the same report notes. The 136,000 deaths reported in 2022 were mostly among children. 

In the United States, we’ve been more fortunate in terms of deaths from measles lately. For example, measles infected 649 people in New York City in a 2018-2019 outbreak and caused serious illness, but no deaths were reported. Public health officials traced the New York City cases to an unvaccinated child returning home from Israel, which was having an outbreak of its own at the time. 

And no deaths have been reported from measles in recent months. That means the 85 people infected in the U.S. since late 2023 survived, although 36 of them had to be hospitalized.

Even though our luck has held regarding deaths, “There are only so many times we can roll the dice,” Ratner said. “There is a big outbreak in the U.K. now. It’s heartbreaking because there are so many things we cannot prevent, but this is something we can.”

Globally, measles kills mostly children in one of two ways: they get measles pneumonia, “which is very difficult to treat,” Schaffner said. “We don’t have anti-measles, antiviral medications for this.” 

The second cause of death is rarer: measles encephalitis. 

Complacency Not the Only Cause

Negative attitudes about vaccination overall could also add to lower immunization rates for measles. Although cases are imported and spread among the unvaccinated, Schaffner said, “What is happening more, however, is children from whom the vaccine is being withheld by their parents go abroad and bring it back home, exposing other unvaccinated children.”

There are political and cultural factors involved in vaccine hesitancy, said Poland, who said he and a lot of his friends had measles as children. He has received funding over the past 30 years to study measles. 

About one to two people die for every 1,000 cases of measles. “This is not something that most parents think about,” Poland said. “Do they want to take that risk or get their child vaccinated?”

The occasional outbreaks in communities across the U.S. remind “us once again that this pathogen is still very much alive and well,” said Jon Woltmann, MD, a pediatric infectious disease doctor at Dayton Children’s Hospital in Ohio. 

People planning international travel might want to discuss the best course of action with their doctor as well, he said. 

Asked what keeps him up at night, Ratner said, “I do worry. We are as a society complacent about measles.” 

The overall vaccination rates in the U.S. are pretty high and help with herd immunity. For example, among school-age kids In New York at the time of the 2019 outbreak, the vaccination rate was 95% to 96%, “which should be good enough to control an outbreak,” he added. 

“But what matters is not the overall rate, but the little pockets where the vaccination rate is 60% to 70%,” Ratner said. “Measles spreads incredibly well, especially within cloistered neighborhoods, which can then endanger larger communities.”