北京市5岁及以上常住人口疫苗接种前新型甲型H1N1流感病毒人群抗体水平分析

Herd immunity against new influenza A（H1N1）in pre-vaccinated residents aged over 5 years in Beijing

目的 了解北京市5岁及以上常住人口接种新型甲型H1N1流感（简称甲型流感）病毒疫苗前的人群抗体水平,为确定防控重点人群提供依据. 方法 2009年10至12月选择未接种疫苗、未明确诊断为甲型流感的北京市常住人口,按照年龄组进行分层,用血凝抑制试验检测新型甲型H1N1流感病毒抗体（简称抗体）,使用抗体几何平均滴度进行不同人群的比较. 结果 共监测3499名调查对象,平均抗体水平为1：8.03,阳性率为11.06%（387/3499）;5～19岁人群抗体水平和阳性率较高,其抗体水平均〉1：8.9,抗体阳性率均〉12%. 结论 不同人群抗体水平受该人群疫情流行强度的影响,学生人群抗体水平和阳性率高与学校疫情流行强度高有关;北京市采取的重点人群和全人群的免疫策略正确,但目前人群免疫力尚未达到理想状态,甲型流感仍有可能在北京市流行.

Objective To explore the herd immunity against influenza A（H1N1）in pre-vaccinated residents aged over 5 years.and therefore to provide data for vaccination policies in high risk populations. Methods From October to December 2009,Beijing CDC conducted a serum survey of the hovel influenza A （H1N1） in the local residents,stratified in 10 age groups between 5 years to over 60 years,without H1N1 vaccination history and disease history.Hemagglutination inhibition （HI） assays were performed at Beijing CDC.Statistical significance was determined with geometric mean titer（GMT）. Results 3499 serum samples were tested for HI antibody.The average level of HI antibody was 1：8.03.and 11.06%（387/3499）were sero-positive（HI antibody level≥1：40）.In the group aged from 5 to 19 years,the level of HI antibody and the sero-positive rate were higber（HI antibody〉1：8.9.sero-positive rate〉12%）. Conclusions The antibody levels in different groups were affected by age specific morbidity,and the higher antibody level of the school-age group was correlated with higher disease intensity in this population.The data showed that the herd immunity in Beijing was under the optimal level,but influenza A（H1N1）would probably become prevalent in the short coming future.