Actually, they will. And they got that immunity without having to risk their lives and health by getting sick. I’ve had mumps, but never the other two diseases because I was vaccinated.
Also, the notion that having measles protects against cancer is bizarre.
Actually there’s a movement to revax everyone who had measles vaccines as kiddo/teens. Because at 50 we aren’t immune anymore.
So, not lifetime.
Realistically vax immunity seriously wanes after 10 years.
Had your tetanus booster lately? :)
Vaccines don’t supply lifetime immunity. Not even close. Having the diseases has given me 50 years of immunity.