According to two papers published in the journal Science Immunology And Science, measles was found to cause the immune system to lose memory. The measles virus is one of the most contagious viruses scientists have ever seen. Before the vaccine was developed in 1963, measles caused between 3 million and 4 million cases in the United States each year.
But over the next few decades, that number plummeted — in 2000, when the United States announced the elimination of the disease, only 86 cases were reported. Since then, however, measles has returned, often in unvaccinated communities.
In one study, researchers analyzed blood samples from 77 unvaccinated Dutch children before and after measles. The results showed that the measles virus removed 11% to 73% of the protective antibodies from these children.
These antibodies could have “remembered” previously infected pathogens to prevent the body from being infected again. This includes a range of viruses and bacteria, from influenza to herpes viruses, to bacteria that cause pneumonia and skin infections.