目的 了解北京市昌平区健康人群流行性乙型脑炎（乙脑）抗体水平，及时发现免疫薄弱人群及疾病传播流行存在的隐患，为制定控制乙脑策略与措施提供科学依据。方法 2017年采取单纯随机抽样方法在昌平区抽取10个村居委会，在当地连续居住6个月以上的10个年龄组人群共360人作为研究对象。采用调查问卷收集研究对象人口学特征、乙脑疫苗免疫史、乙脑患病史等信息。采集其静脉血，采用蚀斑减少中和试验检测血清乙脑IgG抗体。对不同组别间抗体阳性率进行χ²检验。结果 昌平区健康人群乙脑抗体阳性率为93.61%。各年龄组间抗体阳性率差异有统计学意义（χ²=27.053，P<0.05）。不同性别、户籍人群间以及有免疫史人群中乙脑减毒活疫苗不同接种剂次者乙脑抗体阳性率差异均无统计学意义（χ²=0.215、1.283，P>0.05）。接种末剂乙脑减毒活疫苗<1、1～5、6～12年后抗体阳性率差异有统计学意义（χ²=7.220，P<0.05）。结论 昌平区健康人群乙脑抗体阳性率处于较高水平，需加强1岁以下儿童和青壮年人群乙脑防控工作。

Objective To investigate the levels of antibody against Japanese encephalitis (JE) in healthy population in Changping district, Beijing, China, and to find out the hidden troubles of people with weak immunity and epidemic spreading, thus providing a scientific basis for formulating strategies and measures to control JE. Methods A simple random sampling method was performed to collect residents' committees of 10 villages in Changping district in 2017. A total of 360 people from 10 age groups who lived in the local area for more than 6 months were selected as research subjects. Questionnaires were used to collect demographic features, JE vaccine immunization history, disease history of JE, and other information of these research subjects. Venous blood was collected, and serum JE IgG antibody was determined by plaque reduction neutralization test. The positive rates of antibodies of each group were determined by the chi-square test. Results The positive rate of JE antibody in healthy people was 93.61% in Changping district. There was a significant difference in the positive rate of antibodies between different age groups (χ²=27.053, P<0.05). There were no significant differences in the positive rates of JE antibody between different sexes, household registers, and people with immune history inoculated with different doses of live attenuated JE vaccine (χ²=0.215, 1.283, P>0.05). There was a significant difference in the positive rate of antibody between people at <1, 1-5, and 6-12 years after being inoculated with live attenuated JE vaccine (χ²=7.220, P<0.05). Conclusion The positive rate of antibody against JE in healthy population is at a high level in Changping district. It is necessary to strengthen the prevention and control of JE in children under 1 year old and young adults.