The vaccine against Measles is highly effective. The MMR is normally given in 2 doses, one at the age of 1 year and the other at 4 to 7 years. The CDC used to think that only 1 dose was needed for lifetime immunity. Unfortunately it was learned in the 1980’s that some people don’t get enough immunity after just 1 dose at the age of 1 year.
There was an El Al female flight attendant in her early 40’s who got Measles from exposure at work in April 2019. She had had the WHO recommended 1 MMR vaccination when she was a year old back in the late 1970’s. Unfortunately she did not get the second MMR dose recommended after a serious outbreak of Measles in the late 1980’s. In 1991 WHO and CDC recommended a second dose of MMR. I got an additional dose in 1989, because I was living in Houston where there were several thousand cases, so I have the now recommended second dose. Anyway the flight attendant went into a coma in Apri 2019, never regained consciousness, and died in August 2019. As a result of her case of Measles, El Al required all their flight crew to get another dose and set up a vaccination clinic at their hub in Tel Aviv. in short Measles is not a minor disease. It needs to be prevented with very effective vaccines.
I suppose it’s easier to just get another mmr. But, titers can be checked. That’s what they did for me.