Skipping the measles vaccine may put children at risk in more ways than one, new research suggests.
Not only could kids contract measles and suffer its direct effects, they also may sustain measles-induced damage to their immune systems, causing them to experience “immune amnesia” and making them susceptible to other infections they previously were protected against, according to two studies published Thursday.
“Measles virus is much more deleterious that previously recognized,” said Stephen Elledge, a professor of genetics at Brigham and Women’s Hospital and Harvard Medical School in Boston, whose study was published in the journal Science.
Earlier research by one of Elledge’s co-authors, Dr. Michael Mina, an assistant professor of epidemiology and immunology at Harvard School of Public Health, observed that measles appears to suppress the immune system for two to three years after infection, contributing to greater rates of infectious disease and death in children. Other research suggested that the impact may last up to five years. Doctors have also seen that when measles vaccines have been introduced into communities, overall childhood mortality drops, from measles and other causes, too. But the precise reason for these observations hasn’t been clear.
The new research offers an explanation. “There were hints of it from the epidemiological studies, but this really nails it,” Elledge said. “This shows that your immune system is debilitated [by measles], and that means that the measles vaccine is even that much more valuable.”
Measles is a highly contagious disease that causes a telltale rash, fever, cough and other symptoms. In 2000 it was declared eradicated in the United States, but there have been multiple outbreaks since then as the anti-vaccination movement has grown. So far in 2019, more than 1,200 cases of measles have been confirmed in 31 states, the most since 1992, according to the Centers for Disease Control and Prevention.
Worldwide, statistics show that measles affects more than 7 million people and causes more than 120,000 deaths a year. The new findings suggest that broader vaccination could save potentially hundreds of thousands more lives, by preventing deaths from other infectious illnesses that result from the immune damage caused by measles, Elledge and colleagues said.
They studied 77 children in the Netherlands who had not been vaccinated against measles for religious reasons and then contracted the illness during an outbreak. Blood samples taken before they got sick and then two months after they recovered revealed that the measles virus eliminated anywhere from 11 percent to 73 percent of helpful immune-system antibodies that the children had before the infection.
The researchers, however, did not see these immune-system effects in a control group of 33 infants who were studied before and after their first vaccination for measles, mumps and rubella.
“We found that children who were infected with the measles virus had significantly depleted the composition and the number of antibodies to viruses that they had before they were infected with the measles, and so those antibody levels to all those other pathogens just plummeted after the measles,” Elledge said.
The findings indicate that people who contract measles could potentially lose immunity to illnesses they already have been exposed to and developed natural protection against, as well as those they have been vaccinated against, he said. That list could include a range of illnesses such as pneumonia, influenza, rubella, the common cold, hepatitis, rotavirus and human papillomavirus.
The researchers also observed similar findings in four rhesus macaques that were infected with the measles virus and followed for five months.
Mina explained that his paper points to measles causing so-called immune-amnesia by wiping out the immune system’s “antibody factories” known as long-lived plasma cells.
“They live in the bone marrow,” Mina said. “You could think of it like a big jar of marbles. Think of a marble as a little antibody factory. Measles kind of dumps out half of that jar and you have a lot fewer of those little antibody factories to work with.”
In a related study published Thursday in the journal Science Immunology, researchers using the same study population of children from the Netherlands as in the Science study reported on how the measles virus affects immune cells called B cells.
"This study is a direct demonstration in humans of immunological amnesia, where the immune system forgets how to respond to infections encountered before,” study author Velislava Petrova, a researcher at the Wellcome Sanger Institute in the United Kingdom, said in a statement. “We show that measles directly causes the loss of protection to other infectious diseases."
Petrova and colleagues also reported that ferrets infected with a measles-like virus lost some immunity from prior flu vaccination and then had more severe flu symptoms when they were exposed to flu, compared with a group of ferrets that were not exposed to the measles-like virus.
The measles virus is like an accident but for your immune system.
Elledge said that measles' effect on the immune system is similar to what a head injury does to the brain. “If you’re in an accident and you injure your head, you could have some sort of amnesia and impaired function,” he said. “The measles virus is like an accident but for your immune system. It damages your immune system’s memory.”
In essence, the immune system forgets what it once knew, “sort of resetting the clock to an earlier more naïve stage of your life,” he said.
The measles vaccine, however, is like a “seatbelt for your immune system” and those who don’t vaccinate could face risks beyond measles infection, Elledge said. “You’re rolling the dice and if you get unlucky you could get very sick from something that you should have been resistant to because you had the measles.”
Dr. James Cherry, a professor of pediatrics at UCLA’s David Geffen School of Medicine, said the new papers are “superb studies” that offer helpful insights into what doctors and researchers have been observing with measles.
Knowing how devastating measles can be — not only for its direct health effects but also that those infected are more vulnerable to other infectious diseases — the hope is that more people will get their children vaccinated against measles, Cherry said. UCLA is one of the sites that dealt with a measles outbreak earlier this year.
When it comes to not vaccinating against measles, Cherry said, “people who think nature is best are wrong, and that’s the message we have to get across.”
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