> One dose of MMR vaccine is 93% effective against measles, 78% effective against mumps, and 97% effective against rubella. Two doses of MMR vaccine are 97% effective against measles and 88% effective against mumps. MMR is an attenuated (weakened) live virus vaccine.

From:

https://www.cdc.gov/vaccines/vpd/mmr/public/index.html#:~:te....