A Vaccine Against Japanese B Encephalitis Prepared from Infected Chick Embryos

Summary

1. Highly infectious suspensions of embryo tissue have been prepared from embryonated chick eggs inoculated with the Japanese B virus. Infective titers of 10^-7.5 to 10^-8.5 were regularly encountered under suitable conditions.

2. Formalinized vaccines made from 20% suspensions of infected chick embryo tissue are capable of immunizing mice against intraperitoneal infection with the virus of Japanese B encephalitis. Such vaccines are comparable in potency to the Japanese B encephalitis vaccines prepared from infected mouse brain and used by the U. S. Army.