OBJECTIVE: To study the production process of purified Japanese
        encephalitis (JE) vaccine from Vero cells cultivated in roller bottles
        to improve the quality of JE vaccine. METHODS: The 15 L roller bottles
        were used for propagation of Vero cells and JE virus, then the virus was
        inactivated, concentrated, treated by protamine sulphate, purified by
        sucrose gradient density centrifugation and lyophylized as final
        product. RESULTS: Three batches of high quality lyophylized vaccine were
        produced and the quality control tests of vaccine for human use had been
        passed. CONCLUSION: Using roller bottles to cultivate continuous cell
        line-Vero cells for JE vaccine production is feasible.