When you were little you probably got your MMR vaccine and never thought about it again, especially if you grew up in the United States where these illnesses have been largely eradicated. MMR stands for measles, mumps, and rubella (German measles) and is given as a combination vaccine to prevent these three viral infections, each of which poses significant potential health risks.
Travelers are at risk for contracting an infection if they visit someplace where vaccination isn’t widespread. Thus you should make sure you’re properly vaccinated. Most children receive the MMR vaccine when they’re young, but immunity can wane. A simple blood test can tell if you still have immunity from your last vaccination.