一起山区小学流行性腮腺炎暴发疫情调查与疫苗保护效果

Field investigation of a mumps outbreak and evaluation of vaccine effectiveness in a remote village school

目的对一起发生在肇庆市某山区寄宿制小学的流行性腮腺炎暴发疫情开展流行病学调查,评估含腮腺炎成分疫苗(MuCV)的保护效果,为制定疫情防控对策提供参考。方法通过现场个案调查、访谈获得病例资料和疫情相关流行病学信息,运用描述性和回顾性队列研究,分析疫情流行特征,探索危险因素,评价疫苗保护效果。结果共搜索到腮腺炎病例166例,均为学生,腮腺炎总罹患率为7.79%,首发病例2018年10月11日发病,末位病例2018年12月9日发病,疫情持续60 d;年龄集中在10~13岁,占比66.27%;男生罹患96例,女生70例,男女之间罹患率差异无统计学意义(χ^(2)=2.40,P>0.05)。全校34个班级中涉及28个班级,有11个班级罹患率>10%,主要分布在二、四、六年级,不同年级学生的罹患率差异有统计学意义(χ^(2)=96.89,P<0.01);不同楼层之间罹患率差异有统计学意义(χ^(2)=67.35,P<0.01),三楼高于其他楼层。住宿生58名,有12例病例,住宿生患病风险是非住宿生的1.89倍(RR=1.89,95%CI=1.10~3.23);未接种MuCV者罹患率高于接种者(χ^(2)=5.70,P<0.05),VE%(95%CI)=35%(7%~55%);接种1剂次的疫苗保护效果为34%(4%~54%);保护效果随接种时间的延长呈下降趋势(χ趋势2=6.53,P<0.05),接种6年后失去保护效果(χ^(2)=1.12,P>0.05)。结论病例发现和隔离不及时、MuCV接种率低、接种1剂次疫苗的保护效果随时间而减弱导致本次疫情的暴发和持续传播。

Objective To investigate the outbreak of mumps in a remote village school of Zhaoqing City,to evaluate and vaccine effectiveness(VE)of mumps-containing vaccine(MuCV),so as to provide reference for the formulation of epidemic prevention and control strategies.Methods Through on-site case investigations and interviews,case data and epidemic related epidemiological information were obtained.Descriptive and retrospective cohort studies were used to analyze the epidemic characteristics,explore risk factors,and evaluate the protective effect of vaccines.Results Totally 166 cases of mumps were found,and all of them were students.The total attack rate was 7.79%and the outbreak lasted for 60 days.The first case occurred on October 11th and the last case occurred on December 9th in 2018.Most of the cases aged from 10 to 13 years old,accounting for 66.27%.There were 96 male patients and 70 female patients,with no statistically significant sex difference in the incidence rate(χ^(2)=2.40,P>0.05).Involving 28 classes,11 of which had an incidence rate more than 10%,mainly distributed in grades 2,4 and 6.There were statistically significant differences in incidence rates among different grades(χ^(2)=96.89,P<0.01)and different floors(χ^(2)=67.35,P<0.01),with the third floor higher than the other floors.Twelve out of 58 boarding pupils were cases,and boarding pupils were 1.89 times higher in risk of contracting mumps than day students(RR=1.89,95%CI=1.10-3.23).Pupils without being given the shot of MuCV were higher in the infection rate than those having the shot(χ^(2)=5.70,P<0.05),and the VE%was 35%(95%CI=7%-55%).The VE%of one dose was 34%(4%-54%),while the effectiveness of protection was declined with time(χtrend2=6.53,P<0.05).The effectiveness of vaccine almost diasappeared six years after the shot(χ^(2)=1.12,P>0.05).Conclusion Delayed case report and isolation,low rate of receiving MuCV,and decreasing effectiveness of one shot MuCV are closely assocaited with the outbreak and ongoing spread of the epidemic.