Safety and immunogenicity of a freeze-dried, cell culture-derived Japanese encephalitis vaccine (Inactivated) (JEBIK(®)V) in children.

Freeze dried, cell culture-derived Japanese encephalitis vaccine (Inactivated) (JEBIK(®)V) is approved for a three-dose primary immunization followed by a one-dose booster immunization in Japan. We conducted a multicenter, double-blinded, randomized controlled trial of the safety and immunogenicity of the vaccine in 370 healthy children who received three doses of 5, 2.5 or 1.25 μg of virus protein per 0.5 mL formulation subcutaneously. Children received two doses of test vaccine 7-28 days apart followed by a dose 6-12 months after the second vaccination. The three-dose regimen showed a good safety profile with no serious vaccine-related adverse events. Fever and reactions at the injection site were common adverse reactions at each dose of vaccine. The seroconversion rates were 100%, 99.2% and 95.0% after two doses in the 5, 2.5 and 1.25 μg groups, respectively, and 100.0% after three doses in all groups. The geometric mean titers were high for all three formulations after the second and third doses, with a very clear dose-response relationship. These results indicate that JEBIK(®)V is likely to be a useful vaccine.