目的  了解上海地区不同年龄组人群甲型H1N1流感血清抗体水平，对人群中甲型H1N1与2008―2009年季节性流感疫苗株A/Brisbane/59/2007(H1N1)的血清抗体水平进行分析比较。方法  应用常规微量血凝抑制试验（micro-hemagglutination inhibition test, HI）对上海地区不同年龄组（0~5月龄、6月龄~4岁、5~24岁、25~59岁和≥60岁）人群进行甲型H1N1流感抗体检测。各年龄组抗体阳性率的比较采用Pearson χ2 检验和Fisher确切概率法进行分析。结果  上海地区人群甲型H1N1流感血清抗体总阳性率为9.2%（37/404）。不同年龄组中以老年人组（≥60岁）的血清抗体阳性率最高，为25.0%(21/84)；其次是成年人组（25~59岁），血清抗体阳性率为10.0%(8/80)；其他年龄组血清抗体阳性率较低。Pearson χ2 检验结果显示不同年龄组之间抗体阳性率差异有统计学意义。在2008―2009年季节性流感疫苗株A/Brisbane/59/2007(H1N1)抗体阳性的329份血清中有31份甲型H1N1流感抗体阳性，季节性疫苗株抗体阴性的75份血清中有6份甲型H1N1流感抗体阳性。经Pearson χ2 检验分析，这两层人群甲型H1N1流感抗体阳性率差异没有统计学意义。  结论  上海地区人群血清中甲型H1N1流感抗体水平普遍偏低，其中老年人组抗体水平最高，人群对甲型H1N1流感病毒普遍高度易感；季节性疫苗株A/Brisbane/59/2007(H1N1) HI抗体阳性人群血清不能对甲型H1N1流感病毒产生交叉保护抑制。

Objective  To understand levels of antibody to swine-origin influenza A(H1N1) virus (A/H1N1) among different age groups in Shanghai, and to compare the levels between antibodies to A/H1N1 and to 2008-2009 seasonal influenza vaccine virus A/Brisbane/59/2007(H1N1).  Methods  The anti-A/H1N1 antibody levels were determined among 5 age groups (0-5 months, 6 months-4 years, 5-24 years, 25-59 years, and ≥60 years) with routine micro-hemagglutination inhibition test. The positive rates of the antibodies among different age groups were compared by Pearson’s χ² test and Fisher’s exact probability test.  Results  The positive rate of antibody to A/H1N1 in the whole population in Shanghai was 9.2%(37/404). The highest rate was 25.0%(21/84) in the age group of ≥60 years, the next was 10.0%(8/80) in the age group of 25-59 years, the positive rates in other groups were lower. The result of Pearson’s χ² test showed that there were statistically significant differences in the positive rates of the antibodies among different age groups. Of 329 sera positive for antibody to 2008-2009 seasonal influenza vaccine virus A/Brisbane/59/ 2007(H1N1), 31 had anti-A/H1N1 antibodies, and of 75 sera negative for antibody to A/Brisbane/59/ 2007(H1N1), 6 had anti-A/H1N1 antibodies. The result of Pearson’s χ² test showed that there were no significant differences in positive rates of antibody to A/H1N1 between the two types of population.  Conclusions  The anti-A/H1N1 levels in Shanghai population are low, and people are generally susceptible to A/H1N1. The sera positive for antibody to A/Brisbane/59/2007(H1N1) can not provide cross-protection against A/H1N1.