JE-VAX ^® , Japanese Encephalitis Virus Vaccine Inactivated, is a sterile, lyophilized vaccine for subcutaneous use, prepared by inoculating mice intracerebrally with Japanese encephalitis (JE) virus, "Nakayama-NIH" strain, manufactured by The Research Foundation for Microbial Diseases of Osaka University ( "BIKEN_®" ). Infected brains are harvested and homogenized in phosphate buffered saline, pH 8.0. The homogenate is centrifuged and the supernatant inactivated with formaldehyde, then processed to yield a partially purified, inactivated virus suspension. This is further purified by ultra-centrifugation through 40% w/v sucrose. The suspension is then lyophilized in final containers and sealed under dry nitrogen atmosphere. Thimerosal (mercury derivative) is added as a preservative to a final concentration of 0.007%. The diluent, Sterile Water for Injection, contains no preservative. Each 1.0 mL dose contains approximately 500 µg of gelatin, less than 100 µg of formaldehyde, less than 0.0007% v/v Polysorbate 80, and less than 50 ng of mouse serum protein. No myelin basic protein can be detected at the detection threshold of the assay (< 2 ng/mL). Prior to reconstitution, the vaccine is a white caked powder, and after reconstitution the vaccine is a colorless transparent liquid. The potency of JE vaccine is determined by immunizing mice with either the test vaccine or the JE reference vaccine. Neutralizing antibodies are measured in a plaque neutralization assay performed on sera from the immunized mice. The potency of the test vaccine must be no less than that of the reference vaccine.

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