A short version is that your physician can do a blood test that measures the level of antibodies in your blood. If too low, you need a booster. If above a certain level, you're fine. I had it done because I have a number of conditions that would make measles dangerous for me.

Retired PA vaccination is absolutely necessary also was in army medical corp the disease is deadly blood tests can verify immunity only an idiot refuses inoculation unless medical reason like compromised immune system

Got a whole other round of boosters in college as my parents couldn’t find my records. No big deal, it’s about protecting the community I serve. I’ve been immunized 3x for HepB as I seem to have somewhat transient immunity and require titers every year.