Duration of Immunity After a Single Dose of MMR Vaccine
A single dose of MMR vaccine provides long-term—probably lifelong—immunity for measles and rubella in most recipients, though protection is not universal and antibody levels may decline over time. 1
Measles Component
- Approximately 95% of children vaccinated at age 12 months and 98% at age 15 months develop measles antibodies after a single dose 1
- Both serologic and epidemiologic evidence indicate that measles vaccine induces long-term, probably lifelong immunity in most persons 1
- Most vaccinated persons who appear to lose detectable antibody show an anamnestic immune response upon revaccination, indicating they likely retain immune memory 1
- Secondary vaccine failure (true waning of immunity) appears to occur rarely and has little effect on measles transmission 1
- In a 10-year follow-up study, measles antibodies declined moderately after vaccination but remained well above the seropositivity threshold 2
Rubella Component
- Greater than 95% of susceptible persons aged ≥12 months develop serologic evidence of immunity after a single dose of rubella vaccine 1
- Greater than 90% of vaccinated persons have protection against both clinical rubella and viremia for at least 15 years 1
- Follow-up studies indicate that one dose confers long-term, probably lifelong protection 1
- In the 10-year study, anti-rubella antibodies declined moderately but remained well above seropositivity thresholds 2
Mumps Component
- More than 97% of susceptible persons develop measurable antibody following a single dose of mumps vaccine 1
- The duration of vaccine-induced immunity is unknown, but serologic and epidemiologic data collected during 30 years of vaccine use indicate both persistence of antibody and continuing protection 1
- Anti-mumps antibody levels remained relatively stable over 10 years in one study, though protection rates were lower than for measles and rubella 2
- At 10 years post-vaccination, only 73.4% of two-dose recipients maintained protective mumps antibody levels, compared to 93.7% for measles and 83.9% for rubella 3
Critical Clinical Caveats
- The two-dose schedule exists precisely because single-dose protection is incomplete—approximately 5% of children fail to respond to the first dose (primary vaccine failure) 4
- A significant proportion of children show antibody levels below protective thresholds 2-4 years after a single dose: 19.5% for measles, 23.4% for mumps, and 4.6% for rubella 5
- Age at vaccination matters: children vaccinated at ≤15 months show higher rates of seronegativity (20%) compared to those vaccinated at ≥24 months (10%) 6
- Mumps immunity wanes more substantially than measles or rubella, with more than one-quarter of participants showing subprotective levels at long-term follow-up 3
Why Two Doses Are Standard
- The Advisory Committee on Immunization Practices recommends two doses of MMR vaccine separated by at least 28 days to capture the 5% who fail to respond to the first dose 1, 4
- Greater than 99% of persons who receive two doses develop serologic evidence of measles immunity 1
- After a second dose, the proportion negative to one or more antigens drops to less than 4% 5
- The second dose provides a critical safety net for those who did not mount adequate immunity after the first dose 4