流感疫苗在一起学校甲流暴发疫情中的保护效果评价

Effect of influenza vaccination in a school with influenza A outbreak in Sichuan Province

目的了解流感疫苗在学校甲流暴发疫情中的保护效果,为制定疫苗接种策略提供依据。方法选取四川省遂宁市2023年2月发生甲流暴发疫情的射洪市第七小学的全体在校学生作为研究对象。2023年3月9日至12日通过现场发放自填式网络问卷收集流感发病数据,在发病数≥3例的班级学生中选取病例和对照开展1∶2匹配的病例对照研究,查询四川省免疫规划平台核验流感疫苗接种信息。采用χ^(2)检验比较病例组和对照组接种率差异,计算OR值和疫苗保护效果(VE),通过M-Hχ^(2)检验和Pearson相关分析剂量反应关系;采用U检验比较病例的病程天数和症状分值的中位数差异分析流感疫苗对流感病例严重程度的影响(α=0.05)。结果共207名病例和414名对照纳入病例对照研究,当季、近3年内的流感疫苗VE分别为53.08%(95%CI:9.58%~75.65%)、50.12%(95%CI:22.10%~68.06%);近3年流感疫苗接种剂次与发病之间存在剂量反应关系(χ^(2)_(趋势)=7.4,R=-0.11,P<0.05)。流感疫苗对流感病例严重程度的影响分析表明当季接种组较当季未接种组病程中位数由4 d缩短至3 d(Z=2.219,P=0.027),症状分值中位数由10分降低到7分(Z=3.123,P=0.002)。结论当季和近3年接种流感疫苗对预防流感均具有中等保护效果,感染流感的风险随近3年内接种流感疫苗剂次增加而增大,当季接种流感疫苗能有效缩短病程和减轻临床症状。

Objective To investigate the protective effect of influenza vaccine in school influenza A outbreaks,and to provide evidence for the development of vaccination strategies.Methods All students from Shehong No.7 Primary School in Suining City,Sichuan Province,where the outbreak of influenza A occurred in February 2023,were selected.On March 9th~12th,2023,influenza incidence data were collected through on-site self-filling online questionnaires.Cases and controls were selected among students in classes with ≥3 incident cases to carry out a 1∶ 2matching case-control study,and the Sichuan Immunization Planning Platform was queried to verify influenza vaccination information.The difference in vaccination rate between the two groups was compared by χ^(2)tests,the OR value and vaccine effectiveness(VE) were calculated,and the doseresponse relationship was analyzed by the M-H χ^(2)test and Pearson correlation.The U-test was used to compare the median difference between the number of days of illness and the symptom score of the cases to analyze the effect of influenza vaccine on the severity of influenza cases(α =0.05).Results A total of 207 cases and 414 controls were included in the case-control study,and the VE of influenza vaccine of the current season and the past 3 years was 53.08%(95%CI:9.58%~75.65%) and 50.12%(95%CI:22.10%~68.06%),respectively.There was a dose-response relationship between influenza vaccination doses and morbidity in the past 3 years(χ^(2)=7.4,R=-0.11,P<0.05).Compared with the unvaccinated group,the median course of disease in the current season vaccination group was shortened from 4 days to 3 days(Z=2.219,P=0.027),and the median symptom score decreased from 10 to 7 points(Z=3.123,P=0.002).Conclusions Influenza vaccination of both the season and the past 3 years has a moderate protective effect on preventing influenza,and the risk of influenza infection increases with the increase in the number of influenza vaccine doses in the past 3 years.Seasonal influenza vaccination can effectively shorten the course of disease and reduce clinical symptoms.