MMR Immunity After One Dose Does Not Wane Significantly
No, immunity from one dose of MMR vaccine does not disappear after a few years—waning immunity is not a major cause of vaccine failure. 1 The primary reason for recommending two doses is to capture the approximately 5% of people who fail to respond to the first dose (primary vaccine failure), not because immunity fades over time. 1
Why Two Doses Are Recommended
The evidence is clear on this critical distinction:
- Waning immunity has little influence on measles transmission, and the major benefit of the second dose is reducing the proportion of persons who remain susceptible due to primary vaccine failure. 1
- Approximately 5% of children who receive only one dose fail to develop immunity initially—they never mounted an adequate response in the first place. 1
- Almost all persons who don't respond to the first dose will respond to the second dose, which is why the two-dose schedule is so effective. 1, 2
Long-Term Immunity Data by Component
Measles
- Greater than 95% of susceptible persons develop serologic evidence of immunity after one dose. 1
- Antibodies against measles decline moderately after vaccination but remain well above the seropositivity threshold after 10 years. 3
- At 10 years post-vaccination, 93.7% of two-dose recipients maintained protective antibody levels. 4
Rubella
- 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
- At 10 years post-vaccination, 83.9%-100% maintained protective rubella antibody levels. 4
Mumps
- More than 97% develop measurable antibody following vaccination, with approximately 95% efficacy in controlled trials. 1
- Serologic and epidemiologic data collected during 30 years of vaccine use indicate both persistence of antibody and continuing protection. 1
- Mumps shows the most waning: only 69-73% had protective levels at 9-11 years, but a second dose has a genuine boosting effect on mumps antibodies. 3, 4
Critical Clinical Pitfall
Do not confuse low or negative antibody titers with lack of immunity. 2 If someone has two documented doses of MMR vaccine, they are considered immune regardless of serologic testing results, and do not need a third dose. 2 Antibody titers can wane over time without loss of immune memory—the immune system retains the ability to mount a rapid response upon exposure even when circulating antibodies are low. 2
The Bottom Line
- The second dose is not a booster because waning immunity is not the problem—it's a "catch-up" dose for primary vaccine failures. 1
- Revaccination of children who have low levels of measles antibody produces only a transient rise in antibody levels, further confirming that waning is not the issue. 1
- A second dose of MMR vaccine given later in life had only a minor and transient effect on anti-measles and anti-rubella waning titers. 3
The exception is mumps, where a second dose does provide some genuine boosting effect, but even here, the primary rationale for two doses remains capturing initial non-responders rather than addressing waning immunity. 3, 4