Twitter’s been chirping away about some new research on measles! Published in Science, the study looks into why measles causes so much extra disease burden through secondary infections. Previous work has found that measles infection suppresses the immune system, but this effect was thought to resolve fairly quickly after infection, bouncing back within 2-6 weeks.
Turns out, measles is a little more insidious than that. Measles doesn’t just temporarily damage your immune system. There are parts of the human immune system that are geared to respond to new infections, and there are parts which respond to re-infection by a disease you’ve already had and mounted a successful immune response to. When you’re first infected with a disease, the former parts come into play, and that includes inflammation and fever. However, as the infection progresses, your immune system starts to create cells (antibodies) deliberately tailored to seek out and destroy the infectious agent. Even once you’re well again, your immune system keeps a memory cell that can create the antibody again, just in case you ever encounter the same disease in future. If you do, then it quickly creates new copies of the right antibodies, and beats back the infection.
This is how vaccination works: it’s deliberately designed to provoke that immune reaction, so that when you come across the real disease, you can just produce copies of those antibodies, and they’ll destroy the pathogen, usually before you even have time to feel ill.
Measles, however, is a tricky virus because not only can it dampen down the immediate immune response, but it attacks the existing immune memory cells as well. In the study I linked at the start, they found that an unvaccinated child who contracted measles typically lost anywhere from 11% to a critical 73% of their existing antibody repertoire. A child who had and got better from whooping cough could then get whooping cough all over again, after measles infection.
Unsurprisingly, the MMR vaccine does not cause this reduction in immune memory cells, and so it forms a double protection: it protects you from catching measles (and mumps and rubella), but it also ensures you won’t contract a disease that decimates your immune system.
This finding is yet another reason why measles is a really important target for very strict control and ultimately (we can hope) eradication. It isn’t just dangerous on its own (though it is certainly that), but it can make you vulnerable all over again to other dangerous pathogens that you’ve already survived (or been vaccinated for).
In conclusion, please get vaccinated if you can, vaccinate your children unless advised otherwise by a reputable doctor who knows Andrew Wakefield was a scam artist, and remember, vaccines save lives.