Study On The Characteristics And Risk Factors Of Varicella Among Children In Kindergartens And Primary Schools, Qingpu District

Objective(1) To understand the epidemiological characteristics of varicella in Qingpu District from 2005 to 2013.(2) To analyze the characteristics of varicella among children in kindergartens and primary schools in Qingpu District, and compare the Clinical manifestations between breakrough cases and non-vaccinated cases.(3) To study the risk factors of varicella in kindergartens and primary schools in Qingpu District through a case-control study, and provide reference for prevention and control of varicella.Methods(1) A descriptive analysis was conducted for the epidemiological characteristics of varicella in Qingpu District from 2005 to 2013 based on the case data and population numbers. The varicella cases data were collected from China information system of disease prevention and control. The information of resident and non-resident population was collected from Qingpu statistical bureau and police sub-bureau.(2) A matched case-control(1:1)study was designed.The varicella patients were in primary schools and kindergartens, collected from the China information system of disease prevention and control, comparing the Clinical manifestations between breakrough cases and non-vaccinated cases, and the healthy pepole of the control group were chosen around the patients matched in sex in same class.In order to investigate the living habits, social environments and medical history and other related risk factors prior to the onset of illness, the questionnaire was used to the patients and control.(3) Vaccine effectiveness (VE) was used as the evaluation indicator.When the vaccination rate in a population is unknown, case-control studies:VE=(1-OR)X100%.(4) SPSS 17.0 was applied to the whole statistics process.The related statistics methods were chi-square test, t test, conditional Logistic Regression and Cox Regression Model.Results(1) From 2005 to 2013,5375 cases of varicella were reported and the annual average morbidity was 61.16/100000(14.09/100000-113.67/ 100000). The number of cases in annual report was more in November, December, May and June, less in August and February. Qingpu (30.77%),Huaxin (13.45%),Xujing (10.16%) street had the higher incidence in all 10 towns, and the cases among the people aged<15 years old accounted for 71.44%. The incidence ratio of male to female was 1.31:1. A total of 4 varicella related public health emergencies were reported from 2005-2013, which mainly affected primary schools.(2) The incidence ratio of varicella was high in the kindergartens and primary schools, concentrated in the age between 4-8 years old and middle class of kindergartens to grade two in primary schools. Breakthrough varicella cases occurred more in 326 cases, which accounted for 43.25%. There were statistically significant differences (P <0.05) in the duration of the rash, the number of herpes, herpes distribution sites, associated sore throat between breakthrough varicella cases and unvaccinated ones.(3) The overall varicella vaccine effectiveness (VE) was 65.17%(95%CI: 48.18%～76.59%). In terms of kindergartens or primary schools, the vaccine effectiveness of varicella was 88.37%(95%CI:73.84% ～ 94.83%),43.48%(95%CI:6.87%-65.70%)(4) Contact history was a risk factor of varicella and the OR was 2.47(95%CI:1.358～4.495). Immunization history and wash hands were protective factors for the varicella and OR was 0.373 (95%CI:0.241 ～ 0.578),0.313 (95%CI:0.210～0.467)，respectively.Conclusion(1) From 2005 to 2013 totally 5375 cases of varicella were reported in Qingpu District, at a high level in the incidence rate.(2) Overall, the varicella vaccine offers good protection in kindergartens and schools.Varicella vaccine can reduce the clinical symptoms after varricella infection at a certain extent.(3) Effective measures should be adopted, isolating confirmed cases and putting close contacts under medical observation, to further control varicella outbreaks and reduce the public health risk and disease burden of varicella.(4) The state or the high outbreaks province may consider to integrate VarV into the Expanded Program on Immunization. Further studies on varicella vaccine efficacy is recommended. Based on the research findings, the appropriate time of the second dose of VarV will be recommended and varicella vaccination strategies will be adjusted to establish effective immunological barrier.