Impact of different MMR vaccination strategies on mumps incidence in Jiangsu, China: A 20-year interrupted time series analysis based on 180,000 cases.
Abstract
Background
Although China upgraded its mumps vaccine schedule to two doses, quantitative evaluations of real-world, population-level effects remain limited. This study systematically evaluated the immediate and long-term impacts of 1-dose and 2-dose measles-mumps-rubella (MMR) vaccination strategies on mumps incidence in Jiangsu Province.
Methods
Statutory infectious disease surveillance data spanning 240 months from 2005 to 2024 in Jiangsu Province (183,490 cases) were collected. An interrupted time series (ITS) analysis was conducted using a generalized linear model (GLM) based on a negative binomial distribution. We evaluated the intervention effects of the vaccine policies while strictly controlling for autoregression, non-linear effects of meteorological factors, population dynamics, and the intensity of COVID-19 non-pharmaceutical interventions (NPIs). Stratified analyses by age group and geographical region were also performed.
Results
Following the introduction of the 1-dose MMR policy in 2008, no significant long-term downward trend in mumps incidence was observed across the province (IRR = 1.002, P = 0.773), and periodic outbreaks every 3 to 5 years persisted. Following the comprehensive implementation of the 2-dose MMR strategy in July 2020, the overall incidence exhibited a significant accelerated downward trend of 1.0% per month (IRR = 0.990, P = 0.019). Subgroup analyses revealed that the most heavily burdened 5-9 and 10-14 age groups experienced the most significant long-term declines (1.0% and 1.5% per month, respectively). Furthermore, the ≥15 years adult group, which was not directly targeted for vaccination, also showed a long-term reduction (0.9% per month), indicating a significant herd immunity effect. Additionally, the 2-dose policy successfully smoothed out regional incidence disparities, notably mitigating the compensatory outbreaks observed in Northern Jiangsu in 2019.
Conclusion
A 1-dose MMR immunization schedule is insufficient to interrupt periodic mumps outbreaks, and the transition to a 2-dose strategy was associated with a steady long-term decline in overall mumps incidence across Jiangsu Province, providing valuable real-world evidence to support the continuation and optimization of 2-dose MMR immunization schedules.