‘Quite unusual’: Adults make up two-thirds of measles cases in Pennsylvania, presenting unique challenges
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In the late 1980s, John Goldman, MD, was a fourth-year medical resident on his infectious disease rotation when a man arrived at the hospital with fever, conjunctivitis (“pink eye”), upper respiratory symptoms, and a facial rash.
The attending physician asked Goldman what condition these symptoms indicated. At first, Goldman felt stumped. Then the senior doctor reframed the question for the medical resident.
“He said, ‘How could you put this together with something the department of health is concerned about in Chicago?’ I said, ‘measles,’” Goldman, an infectious disease doctor at University of Pittsburgh Medical Center (UPMC) in Central Pennsylvania, told CIDRAP News. “I was part of the outbreak when we realized we had to give a second dose” of the measles, mumps, and rubella (MMR) vaccine.
Almost a case a day
In the early 1990s, Goldman treated another adult with measles in Boston but then didn’t seen a case for 34 years. However, since the start of the Pennsylvania measles outbreak this year, one of the hospitals where he works, UPMC Lititz in Lancaster County, has treated 50 to 100 cases of measles. Three other area hospitals are also treating measles in the county that has the most cases in the state.“We are seeing as many as a case of measles a day,” Golden said. “We typically are getting three, four, five cases a week.”
These patients often reveal that everyone in their home has measles, but the hospital sees only those with infections severe enough to warrant medical attention.
While Pennsylvania’s measles outbreak is the largest in the country, with 1,467 cases, it’s also distinct because two-thirds of cases have occurred in adults. Prior to the introduction of a measles vaccine in 1963, almost all children contracted the viral illness before they were 15 years old. In the recent measles outbreaks in West Texas and South Carolina, more children than adults contracted the virus. And Centers for Disease Control and Prevention data show that only 41% of cases nationwide have involved adults 20 and older.
It is quite unusual to have a measles outbreak with a predominance of adults infected.
William Moss, MD, MPH
“I find this very interesting,” said William Moss, MD, MPH, a professor in the departments of epidemiology and international health at the Johns Hopkins Bloomberg School of Public Health. “It is quite unusual to have a measles outbreak with a predominance of adults infected.”
Perfect conditions for the virus to thrive
Pennsylvania has unique conditions that have allowed the respiratory virus to burn through the adult population.“What’s happening in these communities—particularly these Plain communities in Pennsylvania—is that you have this unusual situation where you have longstanding low vaccination rates, but also no exposure to natural measles,” Moss said. “Then you’re seeing hundreds of cases in adults in Pennsylvania, and it’s not unheard of, but it’s quite unusual to have that phenomenon.”
Moss is referring to traditional Christian groups like the Amish and Mennonites that live a simple life and try to avoid modern technology. Until recently, high rates of vaccination outside the under-vaccinated community likely protected them.
“These adults who were susceptible to measles have been protected by herd immunity,” Moss explained. “Because there was so little measles historically in the United States say over the past 25 years, infectious individuals didn’t enter the community. They weren’t exposed to wild-type measles.”
Goldman notes that the number of people 50 and older with measles in Pennsylvania shows that vaccine hesitancy has been “present for a very long period of time.”
“If you look at when these patients who were infected, making their decision not to be vaccinated, it wasn’t, for the most part, in the last five years,” he said. “It wasn’t with COVID and the rise of vaccine hesitancy we’ve seen across the US. This is a longstanding belief.”
He said there are almost 100,000 members of the Plain community in the state, and the vaccination rate for the community is 20% to 60%.
“I worry that we really don’t have a handle on the number of cases,” Goldman said. “My fear is that the only way that this outbreak is going to stop is when we achieve herd immunity, when 95% of the community has either been infected or vaccinated.”
Alice Yoder, a Lancaster County commissioner, isn’t surprised by the high number of adult cases in the county. Following a measles outbreak in the early 1990s, the county’s MMR vaccination rate increased but started slipping again.
“We were really high—up in the high 90% for years,” said Yoder, a former nurse. “You have generations of people that have not been vaccinated, and they’re growing up. Again, we’re talking about decades of gradually the culture of being unvaccinated passes on from generation to generation.” Lancaster County has 504 of the state’s measles infections, almost 300 more than Mifflin County, which has the second most.
While the Plain community has lower vaccination rates, Yoder believes that vaccine hesitancy throughout the county and state has contributed to the outbreak. “It’s not just the Plain community,” she explained. “It’s really folks that have chosen not to be vaccinated.”
If you look at when these patients who were infected, making their decision not to be vaccinated, it wasn’t, for the most part, in the last five years.
John Goldman, MD
Jeanne Franklin, MPH, the public health director in Chester County—which has the third most measles infections in the state, at 94 cases—suspects that children’s infections are underreported.
“Whole households are getting it,” she said. “If the kids are progressing through the illness and not needing medical care, we don’t know about them. We only know about the people who hit a level of complications that required them to seek healthcare—and that’s when they got tested.”
Complications in adults
Of the six confirmed deaths in Pennsylvania, four occurred in adults. Adults can experience more severe illness, because they tend to have more health conditions.“Like any other viral illness, if you’re older and you’re sicker, you have a higher rate of complications,” Goldman said. “You can get measles encephalitis [brain swelling], measles pneumonia.”
He says they’ve had to intubate patients with measles pneumonia and also care for infected pregnant women giving birth to children with measles. “We’re seeing a surprising number of children that test positive at birth,” he said. “We, fortunately, have not had a lot of those kids get really sick.”
Last month, however, state officials issued an alert about infections at birth, or congenital measles.
It’s unclear if adults will face immune amnesia, which occurs when a measles infection wipes out the immune memory of past infections, Moss said.
“We don’t have good studies of what measles does to the immune system in older adults and whether we see the same state of immune suppression that you see in children,” he said. “It’s certainly possible that adults who have measle are going to be at an increased risk of secondary bacterial infections or other infections.”
People can also have long-term consequences of measles, such as encephalomyelitis, inflammation of the brain and spinal cord following a viral infection. Experts don’t know whether adults can develop the rare, fatal complication called subacute sclerosing panencephalitis, which doesn’t appear for about five to 10 years after infection.
“That I don’t know,” Moss said. “The way I think about the consequences of measles in the adults is that adults tend to have more comorbidities, more underlying conditions that can place them at higher risk of severe measles, and we’ve seen this already in our examples in Pennsylvania.”
Meeting people where they are
Close to the Lancaster County border in the western part of Chester County, people tend to avoid the health department. When measles cases started being reported, Franklin, the county public health director, and her team got to work.“We are doing a pretty traditional and pretty typical public health response,” she explained. “The state is doing the same thing in counties that don’t have a health department.”
Department staff conducts contract tracing and investigations for measles cases. Employees honed communication for the general public and worked with partners in Lancaster to craft messages for the Plain community. In addition, they have been knocking on doors and reaching out to businesses, schools, and community organizations to introduce themselves and offer support. Most important, they’re offering MMR vaccination “whenever and wherever people need it.”
If the kids are progressing through the illness and not needing medical care, we don’t know about them. We only know about the people who hit a level of complications that required them to seek healthcare—and that’s when they got tested.
Jeanne Franklin, MPH
For those in the Plain community, staff offer in-home vaccination. “We have nurses who are in homes every day or every week,” Franklin said. “Transitioning to being able to support more in-home vaccinations wasn’t new or different to us. It just meant we were going to devote some dedicated staff for MMR.”
Staff have vaccinated people in almost 450 homes, with most visits averaging 10 people at a time. One nurse vaccinated 70 people in just one house. “Sometimes they’re inviting their neighbors or their extended families from other homes, which is super cool because we go to one home and we can do [many vaccinations],” Franklin said.
This approach is important because it reaches people who might otherwise struggle to get to the health department. People in the Plain community do not regularly visit doctors, and making a trip can be onerous, especially when people travel with a horse and buggy.
“[They’re] making their livelihood off the land. You can’t just leave,” Franklin said. “The Plain community, it’s not ‘we are against vaccines.’ It’s sometimes they don’t know.”
When one household undergoes vaccination, they often tell their friends and family, which leads to more calls about the vaccine.
“We have people who call us and say, ‘I’d like to talk to someone to come to my family and get vaccinated,’” Franklin said. “Or let’s say a mom and dad get the vaccine, and they call us a week later and say, ‘Hey, we trust this vaccine now because we didn’t feel any ill effects. So can you come back and do our kids?’ That has been word of mouth.”
The health department also receives calls from people in the general public who were vaccine-hesitant but wanted protection against the measles outbreak.
“We had someone come into a clinic and say, ‘Hey, I need to keep a really low profile because I didn’t believe in these, and I don’t want any backlash,’” Franklin said. “[The outbreak] has opened some people’s eyes that have not taken the opportunity to get vaccinated in the past.”
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