So, many people dont know this, but if you ever meet someone who says measles is natural and strengthens the body tell them about immunological amnesia. Measles in unvaccinated people will damage the immune system for a long time.

People that have had a measles infection will have a significantly higher rate of infection for something like 2-3 years post-measles. You can get things like varicella again. Even EBV (missing disease) can re-emerge, and often sensitivity to influenza increases dramatically.

If you have Bern vaccinated against polio, you will usually need another shot.

A friend of mine, an immunologist, use to say: the idea that an infection makes you stronger only ever (if at all) applies to bacterial infections. With viruses "the fewer infections the better" is true enough that I can stand behind it in my professional role. Even common virus infections can mess you up for a long long time.