Acute disseminated encephalomyelitis after treatment with Japanese B encephalitis vaccine (Nakayama-Yoken and Beijing strains).

Seven children with acute disseminated encephalomyelitis (ADEM) after treatment with Japanese B encephalitis vaccine (JBEV) (Nakayama-Yoken strain 1968-88 and Beijing strain 1989-93) were identified by mailed questionnaires and by compilation of previously published case reports. It was considered that encephalomyelitis might have been related to vaccine treatment as the vaccine is derived from mouse brain tissue infected with Japanese B encephalitis virus, a potentially cross reactive antigen. The incidence of severe neurological complications associated with the newer Japanese B encephalitis Beijing strain vaccine seemed to be less than one case per 1,000,000, which is similar to the incidence of neurological complications associated with the older Nakayama-Yoken strain vaccine.