You: "Eh, it's just measles. No big deal."
Science: "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." https://www.bbc.com/future/article/20211112-the-people-with-immune-amnesia