宁波市2010-2014年水痘暴发疫情及其突破病例分析

Epidemiological analysis on varicella outbreaks and the breakthrough cases in Ningbo from 2010 to 2014

目的了解宁波市水痘暴发疫情及其突破病例的流行病学特征,为完善水痘防控措施提供依据。方法对2010-2014年宁波市水痘暴发疫情资料进行描述性分析。比较入学前和入学后以及不同学校类型学生水痘突破病例的初次免疫（初免）至发病时间间隔。结果 2010-2014年宁波市累计报告水痘暴发疫情28起,累计报告病例574例,平均发病率为1.98%（574/28 917）。宁波市水痘暴发疫情主要发生在春季（3-5月）和秋季（9-11月）,分别占32.14%和45.83%。小学是水痘暴发疫情发生的主要场所,占全部暴发疫情的89.29%（25/28）。农村学校水痘暴发疫情共15起,占53.57%（15/28）,平均发病率为2.66%,高于城市学校（1.56%）和城乡结合部学校（1.45%）,P均〈0.01。水痘突破病例中,入学前（1-2岁）接种水痘疫苗者初免至发病时间间隔[（6.38±2.14）年]长于入学后（≥3岁）接种者[（5.31±2.42）年]（t=2.22,P=0.028）;城市小学接种水痘疫苗者初免至发病时间间隔[（7.24±1.83）年]长于县镇小学[（6.46±2.00）年]和农村小学[（5.81±2.03）年]（F=4.67,P=0.012）。结论应重点加强春秋季小学水痘防控工作,尤其应在农村学校中宣传水痘预防知识,并认真开展第2针水痘疫苗接种工作。

Objective To understand the epidemiological characteristics of varicella outbreaks and breakthrough cases in Ningbo,and to provide evidence for varicella prevention and control. Methods A descriptive epidemiological analysis was performed on reported data of varicella outbreaks and the breakthrough cases from 2010 to 2014.The time interval of the initial vaccination and the breakthrough infection was compared among breakthrough cases in preschool and after entrance,and among different types of schools. Results A total of 28 school varicella outbreaks with 574 varicella cases were reported during 2010-2014 with the average incidence rate of 1.98%（574/28 917）.Most varicella outbreaks in Ningbo occurred in spring and autumn,accounting for 32.14% and 45.83%,respectively.And 89.29%（25/28）of varicella outbreaks occurred in primary schools.Fifteen varicella outbreaks occurred in schools of rural areas,accounting for 53.57% of total with the average incidence rate of 2.66%,which was significantly higher than that in urban schools（1.56%）and in urban-rural conjunctive schools（1.45%）（P〈0.01）.Among the varicella breakthrough cases,the time interval was longer among kids vaccinated in preschool（1-2years old）than that after entrance（≥3years）（t=2.22,P=0.028）,and among kids in urban schools than those in rural schools and the urban-rural conjunctive schools（F=4.67,P=0.012）. Conclusions There is urgent need for further prevention and control of varicella among kids in primary schools in spring and autumn,especially in rural schools.The second dose varicella immunization should be addressed seriously among children.