In the mid 70s I contracted measles. I was only 9 or 10 but I think I remember it was because there was a batch of vaccines that didn’t work, or maybe it was do

In the mid 70s I contracted measles. I was only 9 or 10 but I think I remember it was because there was a batch of vaccines that didn’t work, or maybe it was doctors learned we actually needed two doses. Whatever; I’d had the vaccination prescribed at the time, it didn’t work, I got measles. Fast forward 25 years to when I applied to grad school. There was a measles outbreak happening and in order to attend I either needed to have a recent vaccination or a blood test proving immunity. Even though I had natural immunity I just went ahead and got the additional vaccination. It was faster, cheaper, and I didn’t care. The point is, medical knowledge changed. No one made a big deal about needing an extra vaccination. No one made a big deal about even needing certain vaccinations to do things like go to school. Why now?