[Evaluation on the short term effectiveness of two doses mumps-containing vaccine policy in Shandong, China]

Objective: To evaluate the effectiveness of mumps prevention and control after implementation of two doses mumps-containing combined vaccine (MuCV) policy by analyzing epidemiological characteristics of mumps and mumps antibody levels in general population. Methods: We obtained data on cases of mumps reported during 2004-2015 from National Notifiable Diseases Reporting System (NNDRS). Descriptive analysis methods were used to describe the epidemiological characteristics of mumps during 2004-2015. MuCV immunization information from 2005 to 2015 was obtained from the immunization information management system in Shandong Province. Antibody data of mumps in healthy people were from a cross-sectional survey according to the principle of stratified random sampling from 0 to 60 years old healthy people in 2015. Commercial ELISA kits were used to detect and quantify human IgG antibodies against mumps virus in sera, and the results were analyzed statistically. Results: The average incidence of mumps from 2004 to 2015 was 11.43/100 000 in Shandong. The incidence of mumps in the central region (14.64/100 000) was higher than that in the eastern and western regions (11.14/100 000, 11.33/100 000). The incidence of mumps was still high in 2009-2013 (stage of one-dose MuCV free, 16.07/100 000) with the highest incidence of 25.33/100 000 and 24.45/100 000 occurred in 2012 and 2013 and the cases were mainly 6 to 9 years old group (172.67/100 000). Since the second dose MuCV was introduced into NIP for 6 years old children in May 2013 in Shandong, the incidence of mump decreased significantly in 2014-2015 (7.81/100 000), especially in children of 6-8 years old who were vaccinated with two doses of MuCV (2009-2013 was 114.02/100 000; 2014-2015 was 45.66/100 000) and lower than 3-5 years old vaccinated one doses of MuCV. A total of 1 785 serum samples were collected from the healthy population, the average seroprevalence was 80.62% and Geometric Mean Concentration (GMC) was 38.11 IU/ml (95%CI: 37.03-39.19 IU/ml) . There was no significant difference about seroprevalence in different regions, while the GMC in middle region was significantly higher compared to east and west region. The prevalence and GMC in children aged 19 months-2 years and 3-5 years old who received one dose of MuCV were significantly higher than those of <19 months old children. The GMC (46.88 IU/ml, 95%CI: 39.43-55.74 IU/ml) in children aged 6-9 years old who received the two doses MuCV was significantly higher than that of aged 3-5 years old children (31.71 IU/ml, 95%CI: 27.23-36.93 IU/ml). Conclusion: The incidence of mumps in Shandong was still at a high level in spite of coverage one doses MuCV to children. Compared with the period of the 1 dose MuCV immunization strategy, the incidence the groups coverage two doses MuCV was significantly reduced and lower the groups coverage one dose MuCV, but the prevalence and GMC were higher than that of the groups coverage one dose MuCV.