Epidemiological characteristics of breakthrough mumps among children born between 2008 and 2018 in Shapingba District, Chongqing

Objective To analyze the epidemiological characteristics of breakthrough mumps among children in Shapingba District, Chongqing.Methods Breakthrough mumps among children born in Shapingba District between 2008 and 2018 who were vaccinated with mumps containing vaccines (MuCV) were identified through record matching in the China Disease Prevention and Control Information System and the Chongqing Immunization Planning Information Management System. The observation period ended on December 31, 2023. The incidences and epidemiological characteristics of breakthrough cases following 1, 2, and 3 doses of MuCV were compared.Results The overall reported incidence of breakthrough mumps among children born between 2008 and 2018 in Shapingba District was 981.21 per 100,000 (1,189 cases). The reported incidences for breakthrough cases following 1, 2, and 3 doses were 1,747.75 per 100,000 (786 cases), 534.02 per 100,000 (399 cases), and 268.64 per 100,000 (4 cases), respectively, with a statistically significant difference (χ² = 1,364.90, P < 0.001). The mean ages of onset were 5.33 ± 2.15 years, 6.76 ± 1.88 years, and 7.81 ± 2.51 years for cases following 1, 2, and 3 doses, respectively, also showing a statistically significant difference (F = 65.10, P < 0.001). The cumulative reported incidence of 1-dose breakthrough cases rapidly increased from 279.66 per 100,000 at 18 months post-vaccination to 1,471.14 per 100,000 at 54 months. For 2-dose cases, the incidence rose sharply from 57.09 per 100,000 at 36 months post-vaccination to 385.34 per 100,000 at 72 months. For 3-dose cases, the time from vaccination to onset exceeded 51 months.Conclusions The reported incidence of breakthrough mumps in Shapingba District, Chongqing, increased with time since MuCV vaccination. Vaccination with 2 or 3 doses of MuCV significantly reduced the incidence of breakthrough mumps and delayed the age of onset.