It depends on your age and vaccine history. People born before 1957 are presumed immune because nearly everyone caught measles as a child, while people vaccinated between 1957 and 1968 may need another dose because some received an early, less effective inactivated-virus vaccine. Two doses of the MMR vaccine are about 97% effective and one dose about 93%; health care workers, college students, international travelers and close contacts of immunocompromised people should have two doses, and experts say adults in areas with high measles activity should consider a second dose. If you cannot find your records, antibody blood tests exist but are imperfect, and experts say an extra MMR dose is harmless and often cheaper, since most private insurance and Medicaid must cover it at no cost. The question has surged as the U.S. has reported more than 4,000 measles cases in 2026, the most in 35 years.
Source: NPR — Here’s what to know if you’re unsure about your measles immunity status (Oct. 12, 2026)
Image: U.S. Air Force medical personnel administer MMR vaccines. U.S. Air Force photo by Tech. Sgt. Devin Nothstine, public domain, via Wikimedia Commons.