What is 'immune amnesia' and how is it fueled by measles?
A new study from the Harvard T. H. Chan School of Public Health has provided evidence of something epidemiologists have long suspected — that measles may have the potential to nearly wipe out a person’s immune system, leaving them susceptible to other illnesses such as influenza.
“We've known that measles itself can cause immune suppression,” William Schaffner, MD, a professor in the division of infectious diseases at Vanderbilt University tells Yahoo Lifestyle. “But these studies have documented why that occurs — and have given us insight into how long it can affect an individual.”
The research, published in the journal Science on Friday, followed 77 children in the Netherlands who were unvaccinated due to religious reasons. Their immune systems were tested before and after getting measles through what’s called VirScan, a blood test developed by Harvard researcher, and by the lead author on the study, Stephen J. Elledge, MD. Through VirScan, the researchers tested the immune function of the children who had gotten measles and found up to 73 percent of their antibodies were eliminated.
It’s a phenomenon that the researchers refer to as “immune amnesia.” The concept was replicated in a second similar study, published this week in the journal Science Immunology, which found the same mechanism at work in macaque monkeys. The monkeys who were infected with the measles showed a 40 to 60 percent decrease in their antibodies afterward.
“It seems to be that the measles virus itself attacks and destroys — it kills some of the immune cells,” Schaffner says of the studies, which were funded by the National Institutes of Health, Gates Foundation, Value of Vaccination Research Network and other organizations. “We've never known the mechanism for this.”
Michael J. Mina, MD, PhD, one of the lead authors on the study, tells Yahoo Lifestyle the results confirmed a hypothesis first floated in a Science paper he co-authored in 2015, which showed that children who developed the measles had increased mortality for two to three years after their recovery. “We hypothesized that such an immune-amnesia effect might exist to explain the long ‘shadow of death’ that we saw after measles epidemics in the pre-vaccine era,” Mina tells Yahoo Lifestyle.
Before the creation of the measles vaccination in 1963 — according to the Centers for Disease Control and Prevention — an estimated three to four million people became infected with measles annually. Each year, as many as 48,000 were hospitalized, 400 to 500 died and 1,000 suffered severe swelling of the brain called encephalitis. Thanks to the vaccine, measles was officially declared eliminated from the U.S. in 2000. Since 2000, the vaccine has been credited with saving 21 million lives worldwide and reducing deaths by 80 percent, according to the World Health Organization.
But after years without measles, the U.S. saw a surge of cases in 2014, following the rise of a new anti-vaccination movement. The movement, which continues to gain steam, is often connected to a now-retracted 1998 paper in The Lancet by British researcher Andrew Wakefield, which claimed to find a link between vaccines and autism. Although the link has been thoroughly disproven by doctors, the fear that vaccines are dangerous remains — prompting thousands of schools to drop below the recommended vaccination rate this year and the CDC to record the highest number of measles cases since 1992.
Schaffner says that it’s the resurgence of the infection — especially among certain religious groups — that’s allowed researchers to conduct studies like this one as the same effect does not result from the vaccine itself. “The measles vaccine virus does not do this,” he says. “It’s a tamed virus.”
For Mina, the outcome was not entirely expected. “The most surprising results here were definitely the sheer magnitude of the ‘immune amnesia’ effect — even among previously healthy children who had even fairly mild measles infections,” Mina tells Yahoo Lifestyle.
He notes that these results may be even worse for children in developing countries, where measles remain a major cause of death. “In sub-Saharan Africa, for example, those children will have even greater consequences of measles — potentially losing much greater fractions of their pre-existing antibodies and immune memory,” Mina says.
So what does this mean for parents and others concerned about keeping their kids healthy in the U.S.? According to the experts, a great deal. “The biggest takeaway of this study is that measles is really much more detrimental to the immune system and overall childhood health than we had previously recognized,” says Mina. “It not only destroys overall immune function for a few weeks as children recover from the measles virus — something that has been known for a long time — but this study shows that it also prevents children’s ability to defend against pathogens they should have been equipped to deal with over the long term. This study really drives home the real importance of measles vaccination.”
Schaffner, who was not involved in the study, agrees. “The studies were a revelation to me ... they are very elegant science,” he tells Yahoo Lifestyle. “They have provided us information that shows measles is an even nastier disease than we had anticipated. So if you needed yet another reason to get vaccinated, you shouldn't need any more reasons.”
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