目的   探索Vero细胞在无血清条件下制备乙型脑炎灭活疫苗的工艺。 方法   用无血清培养基培养Vero细胞，并将乙型脑炎病毒P3V2株毒种接种于培养的Vero细胞，观察细胞和病毒的生长情况。收获病毒液，通过灭活、纯化制备乙型脑炎灭活疫苗，检测疫苗各项指标，并与有血清培养工艺制备的疫苗（2013年生产的疫苗）进行比较。 结果   无血清培养基培养的Vero细胞生长良好， 培养5 d的细胞呈致密单层生长。3批无血清培养工艺制备的疫苗的第1、2和3次收获液的平均病毒滴度分别为8.847、8.319和7.194 lgLD50/ml。3批无血清培养工艺制备的疫苗半成品的平均抗原含量（1.51 EU/ml）与有血清培养工艺制备的疫苗（1.41 EU/ml）相当，但前者的宿主细胞蛋白含量（19.69 μg/L）则明显低于后者（63.90 μg/L）。 结论   乙型脑炎病毒可在无血清Vero细胞中良好生长，Vero细胞无血清培养工艺制备乙型脑炎灭活疫苗是可行的。

 Objective   To explore a preparation process of inactivated Japanese encephalitis (JE) vaccine with Vero cells cultured by serum-free medium.  Methods   Vero cells were cultured by serum-free medium and JE virus P3V2 strains were inoculated in the cultured Vero cells. The growth of cells and viruses were observed. The virus was harvested, and inactivated JE vaccine was prepared after inactivation and purification of harvest. Various indicators of inactivated JE vaccine prepared by serum-free culture process were detected, and the detection results of inactivated JE vaccine prepared by serum-free culture process were compared with those of inactivated JE vaccine prepared by serum culture process.  Results   Vero cells cultured by serum-free medium grew well, reaching dense layer after 5 days’culture. The average virus titers of 3 batches of single harvested vaccine viruses were 8.847 lgLD50 for the first harvest, 8.319 lgLD50 for the second harvest and 7.194 lgLD50 for the third harvest. The average antigen contents (1.51 EU/ml) of 3 batches of final bulk of JE vaccine prepared by serum-free culture process were similar to those (1.41 EU/ml) of inactivated JE vaccine prepared by serum-free culture process, but the average contents (19.69 μg/L) of host cell protein of the former were significantly lower than those (63.90 μg/L) of the latter.  Conclusion   JE viruses grow well in Vero cells cultured by serum-free medium, and inactivated JE vaccine prepared by serum-free culture process is feasible.