What percentage of individuals over 50 have received the measles vaccine?

Measles Vaccination Coverage Among Adults Over Age 50

Most adults over age 50 in the United States are considered immune to measles and do not require vaccination, as approximately 96.3% of measles cases reported to the CDC from 1985-1990 occurred among persons born in 1957 or later. 1

Immunity Status by Birth Year

Adults Born Before 1957

• Generally presumed to be immune to measles due to natural infection
• CDC data shows only 3.7% of measles cases from 1985-1990 occurred in this age group 1
• No routine vaccination recommended for this population
• Exception: Healthcare workers born before 1957 may be at higher risk
  • Up to 9.3% of hospital workers born before 1957 were found to be non-immune in serologic studies 1
  • 29% of healthcare workers who developed measles between 1985-1989 were born before 1957 1

Adults Born In or After 1957

• Should have documentation of at least one dose of measles vaccine
• Higher-risk individuals (healthcare workers, college students, international travelers) should have two doses 1

Vaccination Recommendations for Adults Over 50

1. General population born before 1957: No vaccination needed unless there's reason to believe they may be susceptible
2. Healthcare workers born before 1957: Vaccination should be offered if susceptibility is suspected
3. Adults born 1957 or later: Should have at least one documented dose of measles vaccine
4. During outbreaks: All susceptible individuals, regardless of age, should be vaccinated

Efficacy of Vaccination in Older Adults

While specific data on vaccination rates in adults over 50 is limited, the MMR vaccine remains highly effective when administered to adults:

• A study of primary school children receiving a second MMR dose 4-5 years after their first dose showed that all but one (92%) seroconverted to measles 2
• The geometric mean titer of measles virus neutralizing antibody increased significantly after revaccination 2

Key Considerations for Clinicians

• Documentation is key: Accept dated records of vaccination, physician-diagnosed disease, or laboratory evidence of immunity
• Outbreak management: During outbreaks, vaccination should be considered for all potentially susceptible individuals, including those born before 1957
• Healthcare workers: Special attention should be paid to immunity status regardless of age
• Travelers: Adults traveling internationally should ensure measles immunity before departure

The presumption of immunity for those born before 1957 is based on the widespread circulation of measles virus before vaccine introduction, which resulted in nearly universal exposure and subsequent immunity in that population.