2019-2020年冬春季麻城市社区季节性流感病毒感染率血清学队列研究

A community-based serological cohort study on incidence of seasonal influenza virus infection in Macheng city from winter 2019 to spring 2020

目的确定社区内有血清学证据的各亚型/系季节性流感病毒感染率,分析影响季节性流感病毒感染的因素。方法在2019年11月(即流感流行季节前)麻城市15个村/街道招募6~59岁居民建立队列,开展横断面基线调查,采集血清,收集人口学及儿童防护知识、行为、态度等信息,在次年7月(即流感流行季节后)进行横断面随访调查,再次采集血清。两次调查配对血清通过血凝抑制(haemagglutination inhibition,HI)试验或微量中和(micro-neutralisation,MN)试验,使用各亚型/系流感病毒流行代表株作为抗原,测定流感病毒特异性抗体,如果抗体有四倍或以上增高,确定为感染。运用单因素和多因素Logistic回归分析感染A(H3N2)、B/Victoria流感病毒的影响因素。结果2019年11月,队列纳入800名研究对象,包括340名6~17岁儿童和460名18~59岁成年人,2020年7月随访到605名研究对象(包括224名儿童、381名成人)并获得了流行季节前后配对血清。25.3%(153/605)的研究对象至少感染过一种亚型/系的季节性流感病毒。儿童各亚型/系流感病毒总感染率为44.2%(95%CI:37.6%~50.8%)显著高于成人的感染率14.1%(95%CI:10.7%~17.7%)。儿童的A(H3N2)流感病毒感染率最高,其次为B/Victoria。流感流行季节前A(H3N2)[OR=0.88(95%CI:0.84~0.93)]、B/Victoria[OR=0.97(95%CI:0.95~0.99)]病毒的MN或HI抗体水平与儿童是否感染该亚型/系流感病毒相关。结论2019—2020冬春季节麻城市6~59岁居民季节性流感病毒感染率较高,近50%的6~17岁儿童感染过季节性流感病毒。流行季节前较高的HI/MN抗体水平可能降低A(H3N2)和B/Victoria流感病毒的感染风险。

Objective To determine incidence of seasonal influenza virus infection in the community and to analyze the factors influencing seasonal influenza virus infection.Methods This study recruited residents aged 6-59 years to build a cohort in 15 villages/streets in Macheng city in November 2019.Meanwhile,a cross-sectional baseline survey was conducted immediately to collect sera,information on demographics and child protection knowledge,behaviors,as well as attitudes using a questionnaire from the participants enrolled in the cohort(i.e.,before the influenza epidemic season).In July 2020,a cross-sectional follow-up survey was conducted to collect sera once again(i.e.,after the influenza season).Paired sera from the two cross-sectional surveys were tested for influenza virus-specific antibodies by hemagglutination inhibition(HI)test or micro-neutralization(MN)test using a circulating representative strain of each subtype/lineage of influenza virus as the test antigen.The infections with influenza virus subtype/lineage was confirmed if there was a four-fold or more increase in titers of antibodies against circulating representative strain of the subtype/lineage of influenza virus.Factors influencing infection with influenza A(H3N2)and B/Victoria viruses were analyzed using univariable and multivariable logistic regression.Results In November 2019,800 study participants were enrolled in the cohort,including 340 children aged 6-17 years and 460 adults aged 18-59 years;605 study participants(including 224 children and 381 adults)were followed up in July 2020 and their paired sera were obtained before and after the influenza season.25.3%(153/605)of the participants were confirmed to be infected with at least one subtype/lineage of seasonal influenza virus by HI and MN tests.The overall incidence of influenza viruses of all subtypes/lineages in children was 44.2%(95%CI:37.6%-50.8%)which was significantly higher than the incidence of 14.1%in adults(95%CI:10.7%-17.7%).Children had the highest incidence of influenza A(H3N2)virus infection,followed by B/Victoria.MN or HI antibody titers in A(H3N2)[OR=0.88(95%CI:0.84-0.93)]and B/Victoria[OR=0.97(95%CI:0.95-0.99)]before the influenza season were significantly associated with whether children were infected with that subtype/lineage of influenza virus.Conclusions The residents aged 6-59 years in Macheng city had a substantial incidence of seasonal influenza virus infection during the influenza season from winter 2019 to spring 2020.Notably,almost half of children aged 6-17 years have been infected with seasonal influenza virus.Higher titers of HI/MN antibodies against seasonal influenza virus before the influenza season would be likely to reduce the risk of infection with influenza A(H3N2)and B/Victoria.