As state health officials monitor a cluster of measles in the Upper Valley, including at least one case in an unvaccinated New Hampshire resident, the state’s top epidemiologist says he wouldn’t be surprised if more cases emerge.

"Given some of the levels of community exposures that we've made public, I think it's very likely there will be other measles infections identified in the coming days or weeks," State Epidemiologist Dr. Benjamin Chan said Thursday.

Measles is extremely contagious, particularly among those who aren’t vaccinated. Chan said he’s especially concerned about the potential spread of the disease given the recent decline in New Hampshire’s childhood vaccination rates.

“The lower the vaccination status, the more unprotected people are — or communities are — and the more likely that if measles is introduced into a community, it can spread person to person,” he said. “And that's what we're experiencing and seeing now.”

So far, health officials have identified three cases in the region: one in New Hampshire, one in Vermont and one in an international traveler who visited Hanover in late June.

Dartmouth Health says anyone who thinks they may have been exposed to measles, or is exhibiting symptoms, can call its hotline at 603-650-1818. Symptoms of measles can include “fever, cough, runny nose, red, watery eyes, and a distinctive red-brown rash,” the health system said in a statement.

Measles can infect nine out of every 10 people exposed to it, if they don’t have any immunity. That’s why experts say at least 95% of the population needs to be vaccinated to prevent outbreaks and achieve herd immunity.

But across the country, vaccination rates are inching downward. Between 2019 and 2022, the share of U.S. kindergartners with the measles, mumps and rubella (or MMR) vaccine fell from 95% to 93%.

New Hampshire doesn’t break out its immunization data for grade schoolers by specific vaccines. But in the most recent school year, just 89% of kindergartners were up to date on all of their required immunizations, including the MMR vaccine. That’s down from 91% to 92% in the years before the pandemic.

That might not sound like much. But with a disease as infectious as measles, Chan said it can have a big impact on whether a community is protected from outbreaks.

“It can spread very easily, and it requires a high level of protection,” he said. “And so those small percentage points do matter.”

New Hampshire requires children to get the MMR vaccine and several other immunizations before they’re enrolled in child care or school, though parents can get exemptions for religious or medical reasons.

The rate of New Hampshire kindergartners exempted from vaccine requirements for religious reasons was 3.9% this year, up from 3% two years earlier.

In 2022, state lawmakers made it easier to obtain religious vaccination exemptions by removing a notarization requirement, though Chan said it’s not clear if that’s responsible for the increase. The use of religious and philosophical vaccine exemptions has been on the rise nationally.

The recent decline in the vaccination rate could come from a few different factors, said Dr. Julie Kim, a pediatric oncologist at Dartmouth Health who heads the American Academy of Pediatrics’ New Hampshire chapter.

Some kids missed routine doctor’s visits during the COVID-19 pandemic, she said. Vaccine hesitancy, for a variety of reasons, is also on the rise.

“Immunizations have become a political issue,” she said, while the “science behind vaccines has been minimized.”

Other parents may simply believe that measles is not much of a threat.

“Measles is actually a much more dangerous disease than people realize,” Kim said.

Outbreaks in undervaccinated communities around the U.S. have caused hundreds of cases in recent years.

About 20% of unvaccinated people who get measles need to be hospitalized, and it can cause long-term complications. About 1 to 3 of every 1,000 children who contract measles die from the disease, according to the Centers for Disease Control and Prevention.

“I think a lot of vaccination right now is about education,” Kim said. “The vast majority of parents actually want to get their kids vaccinated.”

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