学校水痘暴发中水痘疫苗保护率的比较

Comparison of varicella vaccine effectiveness during outbreak in a primary school

目的分析不同接种剂次、不同品种水痘疫苗接种后突破病例（breakthrough varicella,BV）发生率和疫苗保护率（vaccine effectiveness,VE）。方法 2011年10月至2012年1月上海市某小学发生水痘暴发,确认病例为水痘临床诊断病例,收集病例病史资料及全校学生疫苗接种史和既往水痘病史,计算水痘发病率和疫苗保护率（vaccine effectiveness,VE）。结果纳入分析的444名学生,发病29人,罹患率6.5%,水痘疫苗接种率90.8%。有疫苗接种史的学生水痘罹患率低于无接种史的学生,差异有统计学意义（χ^2=8.222,P〈0.05）;疫苗总VE为68.0%（95%可信限为55.2%～80.9%）。接种1剂水痘疫苗学生BV发生率为6.7%,疫苗VE为60.8%（95%可信限为45.1%～76.6%）;接种2剂水痘疫苗BV发生率为0,疫苗VE达100%。接种2剂水痘疫苗的BV发生率明显低于接种1剂,差异有统计学意义（χ^2=5.321,P〈0.05）。接种不同类型（国产、进口、不详）水痘疫苗之间BV发生率的差异无统计学意义（χ^2=1.701,P〉0.05）。结论高接种率的1剂水痘疫苗的接种仍然不能有效阻断学校水痘的传播,接种2剂水痘疫苗能有效降低BV的发生,建议儿童入小学前加强接种1剂水痘疫苗。

Objective To analyze the incidence of breakthrough varicella （BV） and the effectiveness of various doses and kinds of varicella vaccine. Methods The duration of outbreak in a primary school in Shanghai was from October 2011 to January 2012. Medical record of cases as well as vaccination status and history of varicella of all the students in the school were collected, based on which vaccine effectiveness （VE） and incidence were calculated. Results A total of 29 cases were observed in 444 children included in the analysis, indicating an incidence of 6. 5%. The varicella vaccination coverage was 90. 8%. The attack rate of vaccinated children was lower than those unvaccinated （χ^2 = 8. 222, P 〈 0. 05）. Overall VE was 68.0% [95% confidence interval （CI） ： 55.2% - 80. 9%]. The incidence rate of BV of children immu- nized with one dose of vaccine was 6. 7%, while the VE was 60. 8% （95% Ch 45. 1% - 76. 6%）. However, the incidence rate of BV and VE of children immunized with two doses of vaccine were 0 and 100% respectively. The incidence rate of BV of children immunized with two doses of vaccine was significantly lower than that with one dose χ^2 = 1. 701, P 〉 0. 05 ）. Conclusion High vaccination coverage with a single dose of varicella vaccine is insufficient to prevent the outbreak in schools. However, two doses of varicella vaccine may be successful to decrease the BV. A second dose of varieella vaccine in children is recommended before entering primary school.