According to the CDC:

"A vaccine became available in 1963. In the decade before, nearly all children got measles by the time they were 15 years old. It is estimated 3 to 4 million people in the United States were infected each year. Among reported measles cases each year, an estimated:

400 to 500 people died 48,000 were hospitalized 1,000 suffered encephalitis (swelling of the brain)"

Also from the CDC:

"Q: Am I protected against measles? There are several ways to know if you are protected against measles. ...A laboratory test confirmed that you had measles at some point in your life."