Due to the much younger population, most of Africa, India, and Pakistan has had MMR, and it's been found that the mumps vaccine provides significant immunity. In the west most over 35 had measles only, or MR combination without mumps.

DOI: 10.1128/mBio.02628-20

For some reason this hasn't been well covered in the media. I got an MMR booster in June based on preliminary findings, my GP thought I was insane.