MMR Booster Recommendations for Adults
Adults who have previously received MMR vaccine should receive a second dose if they are healthcare workers, postsecondary students, international travelers, in outbreak settings, recently exposed to measles/mumps, or were vaccinated with killed measles vaccine between 1963-1967. 1
Who Needs a Second MMR Dose
The second MMR dose is not technically a "booster" but rather addresses primary vaccine failure in the small proportion who don't respond to the first dose. 1 Most adults born in 1957 or later need only one dose unless they fall into specific high-risk categories. 2
High-Risk Groups Requiring Two Doses:
- Healthcare personnel born in 1957 or later must receive 2 doses of MMR, administered at least 28 days apart 1, 2
- Postsecondary students (college, vocational schools) require 2 doses 3, 1
- International travelers need 2 doses before travel 3, 1
- Adults in outbreak settings or recently exposed to measles or mumps should receive a second dose 1
- Adults vaccinated with killed measles vaccine or unknown vaccine type between 1963-1967 require 2 doses 1, 2
- Adults vaccinated with mumps vaccine before 1979 who are at high risk for mumps infection should receive a second dose 1
Timing Between Doses
- The minimum interval between first and second MMR doses is 28 days (4 weeks) for all adults aged ≥13 years 1, 2
- If inadvertently administered before 28 days, the dose is invalid and must be repeated after the appropriate interval 1, 2
- If more than 8 weeks have elapsed after the first dose, the second dose may be administered without restarting the schedule 1
Evidence of Immunity (No Additional Doses Needed)
Adults are considered immune and do not need additional MMR doses if they have: 1, 2
- Documentation of age-appropriate vaccination (1 or 2 doses depending on risk category)
- Laboratory evidence of immunity to measles, mumps, and rubella
- Laboratory confirmation of disease
- Birth before 1957 (except healthcare personnel, who should still be vaccinated or tested) 1, 2
Critical Pitfalls to Avoid
- Provider-diagnosed disease without laboratory confirmation is NOT acceptable evidence of immunity for any of the three diseases 1, 4
- Birth before 1957 does NOT exempt healthcare workers from vaccination requirements—they need documented immunity or vaccination 1
- Pregnancy is an absolute contraindication—women must avoid pregnancy for 4 weeks after MMR vaccination 3, 2
- Severe immunodeficiency is a contraindication to MMR vaccine 2
Special Consideration for Seronegative Adults
If serologic testing after 2 documented MMR doses shows negative or equivocal titers, additional doses are generally not recommended as documentation of 2 appropriately spaced doses is considered adequate evidence of immunity regardless of subsequent serologic results. 5 Research shows that antibody levels after vaccination may wane over time compared to natural infection, but this doesn't necessarily indicate lack of protection. 6