Scientists have long known that when measles attacks your body, it goes to war against your white blood cells. Specifically, it binds to your B- and T-cells, then wipes them out. B- and T-cells are highly specialized cells critical to your health. They're the ones that recognize infectious germs in your body, then quickly multiply to fight off these unwelcome invaders. A subset of your B- and T-cells also remembers each infection you contract, thus providing you immunity should the infection strike again [sources: Science Museum, Smith-Strickland].
If measles trashes your white blood cells, you're at high risk of succumbing to a host of other infections. The medical community knew this, but thought patients were only vulnerable to other ailments for a few weeks post-measles. What intrigued health officials was the fact that after mass vaccinations occurred in the 1960s, childhood deaths from measles plunged as expected, but so did childhood deaths from a host of other infectious diseases. In resource-poor countries, the drop in childhood death rates post-measles-vaccination was as much as 30 to 50 percent. In some of the poorest nations, it was a whopping 90 percent [source: U.S. National Library of Medicine]. Why was this?
In 2012, researchers finally began to suspect why. A study with macaque monkeys showed that while the monkeys' immune systems began producing new B- and T-cells a month after contracting the measles, these new cells only remembered that the monkeys had had measles in the past. They didn't recall any of the other infections the monkeys had had. Basically, the monkeys' immune systems had amnesia. This meant the primates would have to suffer from all sorts of illnesses again to regain the immunity levels they'd built up since birth [source: Smith-Strickland]. Could the same be true for humans?
It appears so. In 2015, results of a study were published in the journal Science that showed childrenwho got the measles and survived were more likely to subsequently die from another infectious disease than kids who never got the measles. In the four countries studied — Denmark, England, Wales and the U.S. — the children's immune systems all appeared to be weakened for two to three years post-measles. Much like the monkeys, then, contracting measles trashes your immune system for several years after your recovery, making you susceptible to a host of other infections, and even premature death. (The researchers did say that due to the design of the study they could only find a link between measles infection and an increased risk of contracting other infectious diseases, but they couldn't prove a cause-and-effect relationship) [source: U.S. National Library of Medicine].