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Impacts of two-dose mumps-containing vaccine strategy on mumps incidence using segmented regression models
Ning Yao1, Yang Liu1, Yuan-Yuan Zhang1
1EPI Department, Chongqing Municipal Center for Disease Control and Prevention (Chongqing Academy of Preventive Medicine), Chongqing, China.
Objectives:
To evaluate the impact of China's two-dose measles-mumps-rubella (MMR) vaccination strategy on mumps incidence using interrupted time series (ITS) analysis in a megacity of China from 2004 to 2024.
Methods:
Monthly reported mumps case data were extracted from China's National Mandatory Disease Reporting System (NNDRS). Segmented regression models assessed policy effects across three periods: pre-vaccine during 2004-2007, one-dose MMR during 2008 to 2020, and two-dose MMR during 2020-2024. The Newey-West correction is used to address autocorrelation issue (P < 0.01 for Durbin-Watson test).
Results:
Adolescents aged 10-15 years have the highest reported mumps cases across all the years, but with lower case peaks since the two-dose MMR schedule in 2020. ITS analysis revealed a significant downward trend after the two-dose MMR vaccination schedule with a slope change of -0.007 (P < 0.01) and an immediate reduction in cases with a level change of -0.256 (P = 0.056) on log-transformed value. The two-dose MMR policy generated a cumulative effect of reducing 53.76 % mumps morbidity on December 2024 compared to the one-dose policy. Age-specific incidence peaks have been shifted, with adolescents aged 10-15 years remaining to be highest-risk despite vaccination, and breakthrough infections persisted in highly vaccinated school populations.
Conclusions:
The two-dose MMR strategy significantly reduced mumps incidence in the city, supporting its effectiveness for epidemic control. However, persistent cases in adolescents propose consideration of school-based booster programs and enhanced surveillance for emerging strains.
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