Abstract Background The measles, mumps, and rubella (MMR) vaccine is generally considered to provide lifelong immunity against measles and rubella. However, occasional measles outbreaks in countries with high vaccine coverage have raised concerns about waning immunity. In this study, we aimed to estimate the duration of vaccine-induced immunity following MMR2 vaccination in settings where measles and rubella have been eliminated. Methods Using 2019 national serosurvey data, this study estimated antibody waning (decay) rates for each antigen after MMR2 vaccination, with age as a proxy for time since vaccination. In South Korea, MMR2 coverage has exceeded 95% from the 1995 birth cohort, and no significant measles or rubella outbreaks have occurred since 2001, allowing for homogeneous cohorts. Additionally, the time required for the geometric mean titers of each antibody to reach the seronegative cutoff levels was calculated. Results The average antibody decay rates for MMR were 8.71%, 12.02%, and 5.48% per year, respectively, after MMR2 vaccination. The duration of vaccine-induced immunity was estimated to be 19 years for measles, 9.71 years for mumps, and 31.57 years for rubella when equivocal results were considered negative. If equivocal results were considered positive, the duration would be 27.32 years for measles, 15.25 years for mumps, and 39.77 years for rubella. Conclusion Here, we found that individuals who have not experienced natural infection exhibited age-dependent waning of vaccine-induced immunity. While vaccination remains the most effective way to prevent disease, continued vigilance is necessary even in countries with high vaccine coverage.
Chun et al. (Fri,) studied this question.