A second dose of MMR vaccine (or, if they have not been vaccinated, 2 doses given ≥ 28 days apart) is recommended for adults who are likely to be exposed: Students in colleges or other post-high school educational institutions Health care workers born in 1957 or later with no evidence of immunity International travelers Patients with HIV infection, CD4 ≥ 15% and CD4 cell count ≥ 200 / mcL for ≥ 6 months, and no evidence of immunity to measles, mumps, or rubella People born before 1957 are generally considered immune.