Enter “immune amnesia”, a mysterious phenomenon that’s been with us for millennia, though it was only discovered in 2012. Essentially, when you’re infected with measles, your immune system abruptly forgets every pathogen it’s ever encountered before — every cold, every bout of flu, every exposure to bacteria or viruses in the environment, every vaccination. The loss is near-total and permanent. Once the measles infection is over, current evidence suggests that your body has to re-learn what’s good and what’s bad almost from scratch.
“In a way, infection of the measles virus basically sets the immune system to default mode,” says Mansour Haeryfar, a professor of immunology at Western University, Canada, “as if it has never encountered any microbes in the past”.(Source)
I only got halfway in the book “Immune: a Journey into the Mysterious System that Keeps You Alive” by Kurzgesagt and then got distracted and stopped reading (I tend to do that — I’ll pick it up in a few weeks/months when my distractions are gone 🙂 ) — but I highly recommend everyone to read that book. It’s fascinating!