I read this at aarp Dot org:
The good news, according to William Schaffner, medical director of the National Foundation for Infectious Diseases, is that the vast majority of older adults need not worry about contracting (or spreading) the virus. Anyone born in the United States prior to 1957 is considered immune to measles, because almost everyone in that age group was exposed to the virus before a vaccine was available. People born after 1957 who were properly vaccinated, or who contracted measles, are also protected.