Seroepidemiology of Measles and Rubella Among Hong Kong Young Adults and the Humoral Responses of a Measles-Mumps-Rubella Booster Among Participants With Low Antibody Levels

Background Some individuals may not retain adequate immunity against measles and rubella years after 2 doses of measles, mumps, and rubella (MMR) vaccination due to vaccine failure. This study aimed to investigate the rates of vaccine failure and seroconversion by administering an MMR booster to young adults.Methods We first assessed measles and rubella antibody levels using the Luminex multiplex assay, Vitek Immunodiagnostic Assay System (VIDAS) immunoglobulin G assay, and plaque reduction neutralization test among individuals aged 18-30 years who had received 2 doses of MMR vaccine. Participants with low measles and/or rubella antibody levels as confirmed by VIDAS received an MMR booster. Antibody levels were measured at 1 month postbooster.Results Among 791 participants, the measles and rubella seroprevalence rates were 94.7% (95% confidence interval [CI], 92.9%-96.0%) and 97.3% (95% CI, 96.0%-98.3%), respectively. Lower seroprevalence rates were observed among older participants. One hundred thirteen participants who received an MMR booster acquired higher measles and rubella antibody levels at 1 month postbooster compared to baseline.Conclusions Although measles and rubella vaccine failures were observed among 5.3% and 2.7% of young adults, respectively, an MMR booster triggered a significant antibody response. Young adults in Hong Kong had failure rates of 5.3% and 2.7% to measles and rubella vaccines, respectively. One month after an MMR booster, antibody levels against measles and rubella increased significantly, even for participants who had vaccine failures.