The measles vaccine does far more than keep one disease at bay. The human immune system is only as good as its memory, and two separate studies by the same team have now shown that catching the measles virus can give your antibodies 'amnesia', leaving you open to future illnesses.
This means that even once you've recovered from measles, you can potentially lose immunity to other pathogens you've already been exposed to or vaccinated against, including pneumonia, influenza, the common cold, and human papillomavirus.
What's more, this vulnerability can last for months on end, maybe even years.
As such, geneticist Stephen Elledge of Harvard Medical School told NPR we should think of the measles vaccine "like a seat belt for your immune system."
"We know that seat belts protect against head injuries that can cause amnesia," he explains.
"The measles virus is like an accident too - it can give you immune amnesia. Think of the measles like an accident you can prevent in a parallel way."
The two studies looked into the immune systems of 77 unvaccinated children before and after a measles infection, and their results suggest this highly contagious virus infects and cripples the body's immune cells and messes with their memory.
The idea of measles-induced immune amnesia is not exactly new. Studies on non-human primates have shown the virus actually replaces old memory cells with its own alternative, strengthening immunity to measles at the expense of all other pathogens.
Meanwhile, other research reveals measles binds and infects memory T-cells and memory B-cells in the immune system, destroying traces of past infections.
And epidemiologists have shown that, in the pre-vaccine era, measles was associated with as much as 50 percent of all childhood mortality, mostly from immune amnesia rather than measles itself.
"Imagine that your immunity against pathogens is like carrying around a book of photographs of criminals, and someone punched a bunch of holes in it," epidemiologist Michael Mina told the Harvard Gazette.
"It would then be much harder to recognise that criminal if you saw them, especially if the holes are punched over important features for recognition, like the eyes or mouth."
In the first study, measles was found to eliminate up to 73 percent of a child's antibodies and this depletion was not observed in those who had been vaccinated.
Whereas in the second study, researchers found that when macaques were exposed to measles, they lost an average of 21 to 35 percent of their pre-existing antibodies.
"How measles infection has such a long-lasting deleterious effect on the immune system while allowing robust immunity against itself has been a burning immunological question," writes Duane Wesemann of Harvard Medical School in an accompanying editorial.
The good news is that these antibodies can be replenished by vaccine boosters, and the authors suggest children who have contracted the virus make sure to rebuild their immunity this way afterwards.
Since 2018, however, the paper explains that reduced vaccination alone has led to a nearly 300 percent increase in measles infections, and the impact on herd immunity could extend far beyond this one disease.
"This study yet again dispels the dangerous myths perpetuated by homeopaths and other 'natural' healers who claim that exposure of infants to natural infection is important to 'strengthen' children's immune systems," writes endocrinologist Nikolai Petrovsky from Flinders University.