Investigation of an outbreak of varicella in a district of Shenzhen and evaluation of control effect based on SEIR model
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摘要:
目的 采用SEIR模型评估一起水痘暴发疫情处置措施的效果,为今后水痘疫情处置提供科学参考。 方法 回顾性分析广东省深圳市某区一起达到突发公共卫生事件标准的校园水痘暴发疫情资料,使用传播动力学SEIR模型对其防控效果进行评估。 结果 此次疫情共有水痘病例123例,罹患率为3.40%。 其中92人有水痘疫苗接种史。 接种水痘疫苗的总保护率为55.88%,仅接种1剂次的保护率为55.20%,接种2剂次保护率为57.11%,接种1剂次、接种2剂次与未接种人群的发病率差异有统计学意义(P<0.001),接种1剂次与接种2剂次比较差异无统计学意义(P>0.05)。 SEIR模型模拟学校疫情在无干预下自然发展180 d,可产生434例水痘病例,疫情持续101 d,设定对首发病例发病即隔离、对所有病例隔离、首发病例发生后及时进行应急接种的条件下拟合,可产生10、92和31例水痘,疫情持续时间分别为0 d(病例数均小于1)、87 d、35 d;模型拟合学校开展4次水痘疫苗应急接种后可产生80例病例,疫情持续72 d,比实际发生病例数少43例,疫情发生时间少2 d,比接种率90%情况下多49例,疫情持续时间多41 d。 结论 在水痘疫情的处置中,早期发现首发病例、完全隔离病例、及时全面开展应急接种是控制水痘疫情的关键措施。 Abstract:Objective To evaluate the effect of response measures of a varicella outbreak in a district in Shenzhen, and provide evidence for the control of varicella outbreak in the future. Methods The data of varicella outbreak in a school campus in Shenzhen were analyzed retrospectively, and the control effect was evaluated by using SEIR model of transmission dynamics. Results The outbreak involved 123 cases of varicella, with an attack rate of 3.40%. In the cases, 92 had history of varicella vaccination. The overall protection rate of varicella vaccine was 55.88%, the protection rate of only one dose of varicella vaccine was 55.20% , and the protection rate of two doses of varicella vaccine was 57.11% , there was a significant difference in attack rate between group of one dose, two doses and unvaccinated group (P<0.001) . There was no significant difference in attack rate between one dose group and two dose group (P>0.05). The SEIR model simulated that the school varicella outbreak duration for 180 days without intervention, 434 cases of varicella would occur, and the case number tend to be zero on day 101. In the fitted conditions of prompt isolation of the first case, isolation of all the cases, and timely emergency vaccination, 10, 92 and 31 cases of varicella would occur, the duration of the outbreak would be 0 day (the case number would be less than 1) , 87 days, and 35 days, respectively. In the fitted condition of four emergency varicella vaccinations in the school, 80 cases would occur, 43 cases less than actual number, and the outbreak would last for 72 days, 2 days less than actual duration, and compared with the situation under 90% vaccination rate, additional 49 cases would occur and the outbreak would last for another 41 days. Conclusion In the response of varicella outbreak, early detection of the first case, isolation of all the cases and timely emergency vaccination with high coverage are the key measures to control varicella outbreak. -
Key words:
- Varicella /
- Transmission dynamics /
- Emergency vaccination
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表 1 涉疫班级学生接种不同针次水痘疫苗的罹患率比较
Table 1. Comparison of attack rate of varicella in students with different varicella vaccination doses
接种剂次 暴露人数(例) 发病人数(例) 罹患率(%) χ2值 P值 1针 903 60 6.64 0.042 0.837a 2针 503 32 6.36 15.144 <0.001b 未接种 209 31 14.83 13.136 <0.001c 合计 1615 123 7.62 – – 注:a. 1针与2针的比较;b. 1针与未接种的比较;c. 2针与未接种的比较;–. 无数据 -
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