People who should get a measles booster include:

• Older children, adolescents, and adults born after 1957 who have never had measles or been vaccinated, or who lack written proof of immunity. They should get at least one MMR (measles-mumps-rubella) shot

• Individuals who received only one dose of the MMR vaccine (especially those born before 1989 when one dose was standard) may benefit from a second dose to increase protection

• Adults vaccinated between 1963 and 1967 who likely received an inactivated (killed) measles vaccine, which was less effective, should get one or two doses of the MMR vaccine

• People at high risk of exposure, including healthcare workers, students at post-secondary institutions, international travelers, and women of childbearing age before pregnancy, should receive two doses at least 28 days apart if not fully vaccinated

• Anyone 6 months or older living in or traveling to an area with a measles outbreak should be vaccinated regardless of previous status

• Adults unsure of their vaccination or immunity status can get a blood test (IgG antibody test) to determine immunity; if lacking immunity, they should get vaccinated

• People born before 1957 are generally presumed immune due to likely natural infection in childhood and usually do not need vaccination unless they are healthcare workers or at high risk without proof of immunity

In summary, a measles booster is recommended primarily for those without documented immunity, those who received only one dose or an ineffective vaccine, and people at increased risk of exposure