水痘疫苗在学校水痘暴发疫情中保护效果的病例对照研究

目的 评价接种1剂水痘疫苗在学校水痘暴发疫情中的保护效果(vaccine effectiveness, VE)。方法 采用1:2配对病例对照研究，收集中山市2013—2021年水痘暴发疫情调查资料，将病例数≥5例的班的所有病例（共942例）作为病例组，按1:2的比例选取同班、同年龄（±1岁）、同性别的1 884名健康儿童作为对照组，调查其水痘疫苗接种史，采用条件logistic回归分析水痘疫苗保护效果。结果 共调查3～14岁儿童2 826名，儿童接种1剂水痘疫苗的保护效果为58%（95%CI:50%～66%），3～5岁、6～14岁儿童接种1剂水痘疫苗保护效果分别为75%（95%CI:62%～83%）和51%（95%CI:40%～61%）。儿童接种1剂后≤2年、3～5年、6～8年、≥9年的保护效果分别为78%（95%CI:66%～86%）、66%（95%CI:57%～74%）、51%（95%CI:36%～62%）、23%（95%CI:-11%～46%）。儿童接种1剂水痘疫苗的保护效果随接种后时间的延长而降低（趋势χ²=13.071，P<0.001）。结论 儿童接种1剂水痘疫苗有助于防控水痘暴发疫情，但其保护效果随接种后时间的延长而降低，难以阻断水痘传播。建议儿童及时接种2剂水痘疫苗，以预防学校水痘暴发疫情。

Case-control study on the effectiveness of varicella vaccine against varicella outbreak in school

Objective To estimate the vaccine effectiveness (VE) of one dose of varicella vaccine against varicella outbreak in school. Methods Data was collected from 2013 to 2021. A case-control study was conducted with 942 cases from classes with more than 5 cases, compared with 1 884 controls matched by class, age and sex with a ratio of 1:2. Conditional logistic regression was used to estimate odds ratios (OR) in order to further obtain VE. Results A total of 2 826 children were investigated. VE was 58% (95%CI: 50%-66%) in children 3-14 years of age. VE were 75% (95%CI: 62%-83%) in children 3-5 years of age and 51% (95%CI: 40%-61%) in children 6-14 years of age, respectively. VE were 78% (95%CI: 66%-86%), 66% (95%CI: 57%-74%), 51% (95%CI: 36%-62%) and 23% (95%CI: -11%-46%) in children investigated after their immunization of one dose of varicella vaccine for less than 2 years, 3-5 years, 6-8 years, and more than 9 years, respectively. The trend of gradual decreasing of VE over time was statistically significant (χ²=13.071, P<0.001). Conclusions One dose of varicella vaccine provides a satisfactory protection in the varicella outbreak in school, but VE of varicella vaccine attenuates over time. One dose of varicella vaccine in children is not enough to block the transmission of varicella. Children should be vaccinated with two doses of varicella vaccine in time in order to prevent varicella outbreak in school.