一起初中水痘突发公共卫生事件的疫苗保护效果评价

The Vaccine Protection Effect of a Public Health Emergency Caused by Varicella in a Junior High School in Shanghai

目的评价上海市徐汇区2013年某初中水痘突发公共卫生事件中既往水痘疫苗以及应急接种水痘疫苗的免疫效果,为有效控制学校水痘暴发疫情提供依据。方法采用现场流行病学方法收集徐汇区某初中水痘疫情相关资料和该校学生既往水痘疫苗接种史及应急接种情况,计算水痘疫苗保护效果。结果在2013-10-03/12-19该校累计报告27例临床诊断水痘病例,罹患率为3.82%,发病学生主要集中在初二年级,年级水痘罹患率为14.14%。该校707名学生中有558名曾接种水痘疫苗,疫苗接种率为78.93%。经趋势检验,随着年级提升学生水痘疫苗接种率呈下降趋势（χ2=6.56,P〈0.05）。以水痘疫苗接种史为暴露因素,初二年级病例组接种率为66.67%,对照组接种率为76.74%,病例组与对照组暴露比值比（Odds ratio,OR值）为0.50（95%CI：0.21~1.22）,总保护效率为49.62%（95%CI为-22.26%~79.24%）。该校分别于首发病例发病后第13天和第19天对首发班级和全校易感学生进行水痘疫苗的应急免疫,全校应急免疫率为41.38%,应急接种有效率VE应急为53.66%（95%CI为-42.22%~84.90%）。结论该校水痘突发公共卫生事件中,首发病例未及时隔离和疫情期间学校运动会的召开是导致水痘在该校初二年级蔓延的主要原因。水痘疫苗接种距疫情时间间隔过长可能是水痘疫苗未能在本次疫情中起到保护作用的原因之一。在首发病例发病后尽早对易感学生进行水痘疫苗应急接种,可更迅速地形成人群免疫屏障,有效控制暴发疫情。

Objective To evaluate the immunization effect of the history of inoculation of varicella vaccine and emergency inoculation of varicella in a public health emergency in a junior high school in Xuhui district,Shanghai in 2013,and to effectively control the outbreak of varicella epidemic. Methods With field investigation,the relevant data to varicella in a junior high school were collected as well as the history of inoculation history and emergency inoculation were all analyzed to evaluation the protection effect. Results During Oct. 3rd in 2013 to Dec. 19 th in the school,a total of 27 varicella cases were reported,with a occurrence rate of 3. 82%,mainly in grade two students and the grade two occurrence rate of 14. 14%. There were 558 students were received the inoculation of the vaccine,with an inoculation of 78. 93%. With trend chi-test,the vaccine rate showed an increasing trend with the decline of grade level（ χ2= 6. 56,P 0. 05）. Take the inoculation history as the exposure factor,the inoculation rate of the grade two was 66. 67% and the control group was 76. 74%. The OR value of case group and the control group was 0. 50（ 95% CI：0. 21- 1. 22）. The overall protection rate was 49. 62%（ 95%CI： 22. 26%- 79. 24）. On the 13 th and the 19 th day after the occurrence of the first case,all the vulnerable students were inoculated,the immunization rate of the school was 41. 38% and the effective emergency inoculation rate was 53. 66%（ 95% CI： 42. 22%- 84. 90%）. Conclusion In this public health emergency,the main causes include un-timely isolation of the first case and holding of school sports meeting during the epidemic. Emergency inoculation should be timely carried at the occurrence of the first case to rapidly form an immunologic barrier and effectively control the epidemic.