Measles is far more dangerous than most people realize, new research shows.
The disease itself can cause a severe and sometimes deadly illness, but two new studies published on Thursday found that even when patients recover, the virus can inflict lasting harm on their immune systems.
The weakened immunity leaves a child vulnerable for several years to other dangerous infections like flu and pneumonia. The damage occurs because the virus kills cells that make antibodies, which are crucial to fighting off infections.
Scientists call the effect “immune amnesia.” During childhood, as colds, flu, stomach bugs and other illnesses come and go, the immune system forms something akin to a memory that it uses to attack those germs if they try to invade again. The measles virus erases that memory, leaving the patient prone to catching the diseases all over again.
The findings make the need for measles vaccination even more urgent, because it protects children against much more than measles, the researchers said.
“When parents say no to getting a measles vaccine, you’re not just taking a risk of your kid getting measles, you’re causing them to lose this amazing resource of defenses they’ve built up over the years before measles, and that puts them at risk of catching other infections,” said Dr. Michael J. Mina of the Harvard Medical School and Brigham and Women’s Hospital, the lead author of one of the new studies, published in the journal Science. “You’ve got to watch your kid’s back for a few more years.”
In fact if a person who has received vaccinations for other diseases contracts measles, it may wipe out the protection those vaccines had provided. Revaccination could help restore the child’s immunity, the researchers said.
The second study, by a different team, was published in Science Immunology.
“This is wonderful science,” said Dr. William Schaffner, an infectious disease expert at Vanderbilt University, who was not involved in the research. “These are two wonderfully complementary studies that have provided a basic immunologic understanding of a phenomenon that has been recognized for a long time, mainly that measles infection causes immune suppression.”
The studies arrive at a time of heightened concern about measles, as outbreaks flare up in the United States and other developed countries where vaccines had largely eradicated the disease, but where a growing number of parents have begun to refuse vaccination. Some claim religious reasons, and some mistakenly fear a link to autism, based on research that has been discredited as fraudulent.
Globally, the measles vaccine is estimated to have saved 21 million lives between 2000 and 2017. But there are still more than 7 million cases and 100,000 deaths a year, many in developing countries where people lack access to the vaccine. Most who die are children younger than five years.
Vaccination involves two injections, usually given when children are one year old and then four years old. The same shots (commonly referred to as MMR) include vaccines against mumps and rubella, and a newer version also protects against chickenpox.
An ongoing measles epidemic in the Democratic Republic of Congo has killed more people than that country’s current Ebola outbreak. Since January, there have been more than 203,000 measles cases and about 4,100 deaths, mostly in young children, according to Unicef.
The two new reports are based on studies of 77 children from Orthodox Protestant schools in the Netherlands who, for religious reasons, were not vaccinated. The researchers took blood samples to test their immune systems before and then about two months after they caught measles during a 2013 outbreak.
To profile each person’s past exposures to infectious disease, the authors of the Science study used VirScan, a tool that can detect antibodies to hundreds of viruses and many types of bacteria. The tool was developed by Stephen J. Elledge, the study’s senior author and a geneticist at the Harvard Medical School and Brigham and Women’s Hospital.
Comparing the before-and-after samples, the test found that measles wiped out 11 percent to 73 percent of a child’s antibodies against an array of viruses and bacteria. Dr. Elledge called the depletions shocking, and said that the biggest drops tended to occur in children with the severest cases of measles.
Dr. Mina said that the decreases occurred because the virus killed “long-lived memory cells,” which reside in the bone marrow and can live for decades. He called the cells “precious factories” that churn out antibodies.
He and Dr. Elledge said that children could rebuild the immunity they had lost, but only by being exposed to infections again, or being vaccinated.
They also tested babies who had been vaccinated against measles, and found no decreases in their antibody levels, even though the vaccine contains live (but weakened) viruses. The vaccine virus is somewhat different from the natural one, and does not invade the crucial antibody-making cells.
To study the effects of measles infection for longer than the longer than they had in the Dutch children, the team tested four macaque monkeys before and after infecting them with measles. The animals lost 40 percent to 60 percent of their antibodies, and the loss persisted for at least five months.
The study was paid for by the Value of Vaccination Research Network, the Gates Foundation, the National Institutes of Health and several European research organizations.
The second study, led by Velislava N. Petrova from the Wellcome Sanger Institute in Britain, tested samples from 26 of the same unvaccinated children from the Netherlands. The researchers used genetic sequencing to study the immune system’s B-cells, which are involved in making antibodies. They found that key players, memory cells that had formed to fight specific diseases, went missing. Another type of B-cell was also depleted, leaving the immune system in what the scientists called an immature state.
That research was paid for by Wellcome as well as research organizations from Indonesia and Germany.
“These elegant studies provide insights into immunological deficits following measles infections that have intrigued scientists for over 100 years,” said Dr. Ian W. Lipkin, director of the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health.
“I agree that the findings also enhance the strength of the argument for vaccination,” he said but added, “I don’t think it’s going to change vaccination rates, because those decisions are irrational.”
Researchers first noticed a century ago that measles seemed to suppress the immune system, but they didn’t know how. Dr. Clemens von Pirquet, an Austrian scientist, reported in 1908 that a child who’d had a positive skin test for tuberculosis — an immune reaction indicating past exposure — tested negative after contracting measles.
Dr. Mina said there were scattered reports in medical journals over the years that psoriasis, a skin disorder caused by an immune reaction, cleared up in children after a bout with measles.
He was an author of a 2015 article in Science that looked at disease patterns in several countries following measles epidemics before vaccines were developed, and found that illnesses and deaths from other infectious diseases increased for as long as five years after the outbreaks. That study suggested that the measles virus may have been linked to up to 50 percent of childhood deaths from infectious diseases, mostly illnesses other than measles itself.
“This emphasizes again what a nasty infection measles is,” Dr. Schaffner said. “We know that in and of itself it can lead to ear infections, pneumonia and encephalitis. It remains in the developing world a leading cause of death among children. This makes it clear that measles has detrimental effects beyond measles itself. If we wanted, if we needed even more reason to protect our children with measles vaccine, here’s some more information you ought to think about.”
