The measles vaccine can protect against more than just measles

Infection with measles can hurt the immune system's memory of how to fight other diseases.

When a child gets their measles vaccination, they’re protected against a highly contagious disease that can be deadly. But new research confirms that when they don’t get the measles, they’re also less at risk of getting a host of other infectious diseases. That’s because measles, in addition to making them sick, knocks out their immune system’s memory of how to fight against other illnesses, according to two papers published today.

“This will help with developing a new understanding of the benefits of measles vaccines to society,” says Michael Mina, author on one of the papers, published in Science, and an assistant professor of epidemiology at the Harvard T. H. Chan School of Public Health. “The measles virus is much more dangerous than we knew, and that makes the vaccine even more valuable.”

In 2015, Mina conducted an analysis showing that, historically, childhood measles outbreaks were closely followed by increases in deaths from other, non-measles illnesses. Based on that finding, he hypothesized that measles created an “immune amnesia”—it wiped out the body’s recollection of how to fight diseases its encountered before. Mina spoke with public health groups like the World Health Organization and the Centers for Disease Control after publishing that study. “All those conversations ended with some comment like, we really need to get at the biological mechanisms for this,” he says.

To find out, Mina tested blood samples from 77 children in the Netherlands who had the measles and were not vaccinated. They tested them using a new tool called VirScan, developed by study author Stephen Elledge, a professor in the department of genetics at Harvard Medical School and Brigham and Women’s Hospital. The tool can measure antibodies present in a blood sample—an indication of which viruses the body has been exposed to and is therefore better equipped to handle in the future. “Antibodies are great reporters on the health of the immune system, and the breadth of the immune system,” Elledge says.

The team found that, after they were sick with the measles, the children lost between 11 percent and 73 percent of their existing antibodies. On average, they also lost 20 percent of their antibody diversity. An experiment in macaque monkeys showed something similar: After a measles infection, the antibody loss was still present five months later.

The large variation in the percentage of antibody loss wasn’t surprising, Mina says. “We’re worried that degree of variation is the best case scenario. In places where children might be malnourished going into a measles infection, we suspect that we might see a higher degree of immunological memory loss than we saw here.”

Another study, published today in Science Immunology, found that children with previous measles infections were missing key types of immune cells, and specifically, immune cells that could respond to specific diseases.

The studies complement each other, and they “break open and elucidate the pathway of how a child becomes immune-compromised after measles, and it’s pretty devastating,” Jennifer Lighter, a pediatric infectious disease physician and epidemiologist at NYU Langone Medical Center, told the Washington Post.

Mina and Elledge’s ViraScan antibody study was also able to show that kids who were infected with measles, and then infected with a new virus they had never encountered before, responded normally. That’s a sign, Mina says, that the measles virus did not impact the immune system’s ability to fight off a new disease—it just removed the protection that a child might have had against a disease that they’d seen before. “It’s immune memory, and not the cells ability to respond in the future,” he says.

The findings indicate that future clinical research should look for ways to mitigate the long-term immune damage after a child gets the measles, Mina says. For example, these kids might need to be re-vaccinated for conditions that they might have been vaccinated against before.

“Hopefully, this new research can really clarify that [not vaccinating] is not just allowing a kid to get a rash, but it’s playing russian roulette with their health,” he says. “Every time they’re re-exposed to a new pathogen, they might have a much more severe reaction.”