Immunity amnesia Why measles is so dan erous
Getting infected with measles is much more dangerous than scientists once suspected. In addition to the illness caused by the virus, a measles infection also takes a wrecking ball to the immune system. It destroys up to half of the existing antibodies that protect against other viruses and bacteria, according to research published yesterday.
That means people, especially children, who get measles become much more vulnerable to other germs that cause diseases such as pneumonia and influenza that they had previously been protected against.
The discoveries have enormous and immediate public health implications, researchers and clinicians said, and underscore more than ever the importance of measles vaccination. In recent years, anti-vaccine misinformation has been one reason vaccination rates have plummeted and global measles cases have surged. This year, the United States has had 1250 cases of measles, the most since 1992.
Measles is not a harmless illness, as some anti-vaccine activists falsely claim, but one with deadly consequences. Most people, even doctors, have never seen the consequences of the disease because it became so rare thanks to vaccination and was declared eliminated in the United States in 2000.
‘‘The big thing we show here is that even if a child gets through measles – and you have to be lucky to get through the measles infection – you’re setting your kid up to be at increased risk to all these other infectious diseases that they could encounter on any given day,’’ said Michael Mina, an infectious disease epidemiologist at Harvard’s T.H. Chan School of Public Health and lead author of the first study, published in Science.
More than 7 million people are estimated to have been infected with measles in 2018, according to global health officials. Comprehensive coverage with measles, mumps, rubella vaccine would prevent more than 120,000 deaths directly attributed to measles this year, and it could also ‘‘avert potentially hundreds of thousands of additional deaths attributable to the last damage to the immune system,’’ the authors wrote.
Mina and investigators from Harvard Medical School, Brigham and Women’s Hospital, analysed blood samples of 77 unvaccinated children before and two months after a measles outbreak in 2013 in their Netherlands community, which is religiously conservative and opposed to vaccination. Using a tool that tracks antibodies, they found measles infection wiped out 11 per cent to 73 per cent of different antibodies that ‘‘remember’’ past encounters with germs and help the body avoid repeat bouts of influenza, herpes virus, pneumonia and skin infections.
No loss of antibodies was observed in children vaccinated against measles, mumps and rubella.
Mina and his colleagues found that those who survive measles gradually regain their previous immunity to other viruses and bacteria as they get re-exposed to them. But the process may take months to years. In the meantime, people remain susceptible to serious complications of those infections, he said.
A second study, in the journal
Science Immunology, analysed the antibodies collected from blood samples of 26 children from the same group of unvaccinated Dutch children.
Researchers from the Wellcome Sanger Institute, University of Amsterdam and their collaborators sequenced their antibody genes and found that specific immune memory cells were no longer in the blood of two children after measles illness, leaving them vulnerable against infectious diseases they had previously been protected against.
Past studies suggested that the measles virus wipes out a significant portion of essential immune memory cells that protect the body against infectious diseases, creating ‘‘immune amnesia.’’
The findings by the two international teams of researchers are the first to measure how that damage occurs.
Doctors who treated children during New York City’s measles outbreak this year are starting to see children getting subsequent severe infections that require hospitalisation. New York’s outbreak was centred in the ultraOrthodox Jewish community that was targeted by anti-vaccine activists. Many parents were reluctant to get their children vaccinated against measles.
The two studies ‘‘break open and elucidate the pathway of how a child becomes immune-compromised after measles, and it’s pretty devastating,’’ said Jennifer Lighter, a pediatric infectious disease physician and epidemiologist who helped lead the measles response at NYU Langone Medical Centre and was not involved in either study. Fifty children were treated at NYU Langone; about half were admitted. The measles, mumps and rubella vaccine, or MMR, ‘‘clearly has protection much greater than we previously recognised,’’ she said.
At least three children who had measles developed subsequent severe infections, Lighter said.