Abstract
WHAT IS ALREADY KNOWN ABOUT THIS TOPIC? The Measles-Mumps-Rubella (MMR) vaccine plays a crucial role in preventing mumps. Before the implementation of the two-dose MMR vaccine policy, baseline data on mumps virus antibody seroprevalence and geometric mean concentrations (GMCs) among children and adolescents in Fujian Province were available. WHAT IS ADDED BY THIS REPORT? This report provides a post-policy evaluation following the introduction of Fujian's two-dose MMR policy in June 2020. The 2023 survey shows an overall seroprevalence of 79.53% and a GMC of 265.61 U/mL. Compared with 2018, significant improvements were observed in children under 2 years; however, a concerning decline was noted among adolescents aged 15-17 years. Antibody levels peaked shortly after vaccination, and two doses were found to confer significantly higher immunity than one dose within a 270-day period. WHAT ARE THE IMPLICATIONS FOR PUBLIC HEALTH PRACTICES? The two-dose MMR policy has been effective in improving early childhood immunity. However, the observed waning immunity in adolescents underscores the urgent need for ongoing serological surveillance, particularly in individuals aged 6-19 years, to inform potential recommendations for booster vaccinations.