Studies have shown that measles causes long-term damage to the immune system, leaving children who were susceptible to other infections long after the initial disease has passed.
Two studies of unvaccinated children in an orthodox Protestant community in the Netherlands have shown that measles erases the memory of the immune system from previous diseases, restoring it to a child-like condition, and also leaving the body less prepared to fight new infections.
Studies have shown that measles has eliminated 11% to 73% of protective antibodies to children.
"We have found really strong evidence that the measles virus is actually destroying the immune system," said Professor Stephen Elledge, a geneticist at Harvard Medical School and co-author of one article. "The threat that measles poses to humans is far greater than we previously imagined."
Worldwide, measles affects over 7 million people annually and causes over 100,000 deaths. The reduced vaccination rate has led to an almost 300% increase in measles since 2018.
The United Kingdom has recently lost its measles-free status due to a decrease in the percentage of MMR immunizations (measles, mumps and rubella). Coverage of 95% of the population is considered necessary to prevent outbreaks. Among 24-month-old children in England, the number of vaccinations fell from 91.2% in 2017-18 to 90.3% in 2018-19, which is the lowest rate since 2010.
Measles is highly contagious and can spread when someone with a virus coughs, sneezes or exhales. Inside the airways, the virus passes into the immune cells that are on the border between the lungs and the blood. From there, the virus replicates and spreads to immune cells throughout the body.
Earlier, scientists have deduced a long-term effect on the immune system because there has been an increase in deaths due to other infections after measles and because the virus directly attacks the immune system. The latest work reveals the extent of damage for the first time.
The researchers recruited volunteers from three schools in the Netherlands. They took blood samples from healthy, unvaccinated children aged 4 to 17 years, followed by 77 children who were infected with the measles outbreak in 2013, to repeat the samples.
The first article, led by Velislav Petrov, of the Wellcome Sanger Institute and Cambridge University, says that measles destroys two separate defense lines of the immune system.
To deal with previously unseen infections, the immune system relies on constantly pumping out a diverse range of immune cells – thousands of different varieties, each with slightly different receptors on its surface, with a collective ability to recognize almost every pathogen.
"The more diverse their scope, the better," said Petrova. However, after measles, the children had a much more limited range.
The immune system also creates long-lasting memory cells that are in constant circulation, allowing the body to quickly recognize and eliminate previous infections.
However, after measles, a significant proportion of the immune memory cells disappeared from children's blood, which scientists described as "immune amnesia." It can even mean that children with measles may need to be revaccinated because of previous illness.
"We show that measles directly causes loss of protection against other infectious diseases," said Petrova.
The children participating in the study were seen about six weeks after measles infection, so it is not yet clear how long it will take to restore the immune system.
"It can be speculated that it is very likely that he will recover based on the recovery seen in people taking immunosuppressants," Velislava said. "Maybe you'll recover after five years."
Elledge looked at antibodies in the blood (proteins produced by immune cells) and found that 11-73% of the antibody memory bank was erased after measles.
The study showed that the MMR vaccine itself did not cause immune suppression, which means that recipients benefit from lifetime resistance to measles infection without the harmful effects of natural infection.
Petrova said dealing with skepticism about vaccines is a complex task. "We shouldn't think that scientific data is enough to convince people," she said. "We need to provide enough reliable information to people in the place of care. Don't create polarization around this in society. "
Jonathan Ball, a professor of molecular virology at the University of Nottingham who was not involved in this work, said: "In our current climate of falling vaccine collection rates, this is a timely reminder of why MMR immunization is so important – it not only protects against vaccine viruses is intended, but also prevents complications that can occur after measles infection. "