Adults born before 1957 do not need the MMR vaccine. The explanation for this recommendation is that nearly every person born before 1957 contracted the actual diseases when they were young and are thus presumed immune to measles, mumps, and rubella.
Adults born during or after 1957 should receive at least one dose of the MMR vaccine if they did not receive it in the past. Certain adults should receive a booster dose, which needs to be given more than four weeks after the first dose. People who should receive a booster dose include college students, healthcare workers, international travelers, and people exposed during a measles or mumps outbreak.
It is very common for pregnant women to have their blood drawn to see if they are immune to rubella. If they are not immune, they are usually given an MMR vaccine after the birth of their baby. However, the position of many vaccine experts is that if the pregnant woman has clear documentation that two MMR vaccines were given in the past, then the result saying that she is not immune is probably wrong and she does not need a booster.
If a woman is planning to become pregnant in the future and is not sure if she received two MMR vaccines in the past, she can have her blood drawn to see if she has immunity to rubella. If she does not have the necessary antibodies, she could then receive one (if only a low level of antibodies is present) or two MMR vaccines before she becomes pregnant.
Remember that she should wait at least twenty-eight days after the last MMR vaccine before becoming pregnant in order to avoid the theoretical risk of transmission of a live virus to her fetus.