What are the indications for a second dose of Measles, Mumps, and Rubella (MMR) vaccine in adults?

Indications for MMR Second Dose in Adults

A second dose of MMR vaccine is recommended for adults who are students in postsecondary educational institutions, work in healthcare facilities, or plan to travel internationally, administered at least 28 days after the first dose. 1

Primary Indications for Second MMR Dose

Adults who should receive a second dose of MMR vaccine include:

• Students in postsecondary educational institutions 1
• Healthcare workers 1
• International travelers 1
• Adults who were previously vaccinated with killed measles vaccine or measles vaccine of unknown type between 1963-1967 1
• Adults in outbreak settings or recently exposed to measles 1
• Adults vaccinated with mumps vaccine before 1979 (either killed mumps vaccine or mumps vaccine of unknown type) who are at high risk for mumps infection 1

Special Considerations

Healthcare Personnel Born Before 1957

• For unvaccinated healthcare personnel born before 1957 who lack laboratory evidence of immunity or disease confirmation, healthcare facilities should consider routinely vaccinating with 2 doses of MMR vaccine for measles and mumps protection, or 1 dose for rubella protection 1

Timing Between Doses

• The second dose of MMR should be administered a minimum of 28 days after the first dose 1
• This minimum interval is important for optimal immune response 2

Evidence of Immunity

Adults are considered immune to measles, mumps, and rubella if they have any of the following:

• Documentation of age-appropriate vaccination (≥1 dose of MMR for most adults, 2 doses for those in high-risk groups) 1
• Laboratory evidence of immunity 1
• Laboratory confirmation of disease 1
• Birth before 1957 (except for healthcare personnel) 1

For rubella specifically, documentation of provider-diagnosed disease is not considered acceptable evidence of immunity 1.

Rationale for Second Dose

The second dose of MMR vaccine is recommended because:

• A significant proportion of individuals may have inadequate immunity after a single dose, particularly for measles and mumps components 3, 2
• Studies have shown that 19.5% and 23.4% of children had measles and mumps antibody levels below protective thresholds 2-4 years after their first MMR dose 2
• Mumps outbreaks have occurred in highly vaccinated populations, suggesting waning immunity over time 3
• A second dose reduces the proportion of individuals negative to one or more antigens to less than 4% 2

Safety of Second/Third Doses

• The second dose of MMR vaccine has been shown to be safe and well-tolerated 4
• Even a third dose of MMR (when given in outbreak settings) has demonstrated an acceptable safety profile with mostly mild and transient adverse events 5

Common Pitfalls and Caveats

• Do not assume adults born before 1957 are immune if they are healthcare workers - consider testing for immunity or vaccinating 1
• Do not accept documentation of provider-diagnosed disease as evidence of immunity for rubella (or for measles and mumps in more recent guidelines) 1
• Do not administer MMR vaccine to pregnant women or those planning to become pregnant within 4 weeks 1
• Do not miss the opportunity to vaccinate women of childbearing age who lack evidence of rubella immunity 1
• Remember that waning immunity to mumps may occur even in previously vaccinated individuals, making the second dose particularly important for this component 3