Effectiveness of mumps-containing vaccines and the risk of breakthrough infection in China: A systematic review and meta-analysis

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Objective To evaluate the vaccine effectiveness (VE) and breakthrough infection risk of mumps-containing vaccine (MuCV) in China through a systematic review and meta-analysis. Methods Following the PRISMA guidelines, cohort studies on MuCV VE in China published between 1990 and 2025 were systematically retrieved from four electronic databases (CNKI, Wanfang, PubMed, and Web of Science). VE was calculated using a random-effects model of R software. Multivariable meta-regression analysis was performed to assess the impact of various factors on the risk ratio (RR) of breakthrough infection. Results A total of 69 studies from 65 articles were included. The overall VE of MuCV was 74%, with values of 64% for one dose, 70% for two doses, and 81% for three doses. Compared with one dose, two or three doses of MuCV significantly reduced the risk of breakthrough infection(RR 2 doses = 0.61, P = 0.004; RR 3 doses = 0.35, P < 0.001). With longer interval since vaccination, the risk of breakthrough infection significantly increased (reference: ≤3 years, RR 4–5 years = 1.12; RR 6–10 years = 1.35; RR >10 years = 1.86, P < 0.001). Outbreak cases had a higher breakthrough infection risk than sporadic cases (RR outbreak = 2.16, P = 0.002). Emergency vaccination significantly reduced the risk of breakthrough infection compared with routine vaccination (RR emergency = 0.63, P = 0.045). The risk of breakthrough infection did no differ significantly across different study populations (reference: middle school students, RR daycare = 1.15, RR elementary = 1.20). Conclusions MuCV demonstrates good protective effect against mumps virus infection, but VE wanes over time after vaccination. The number of doses, interval since vaccination, case classification, and vaccination strategy significantly affected breakthrough infection risk.