Japanese B encephalitis is a mosquito-borne disease. The majority of infected patients are asymptomatic bus severe cases could be found with high fever, drowsiness,
loss of consciousness, seizure and death from brain tissue infection. Survivors are usually left with brain damage and severe physical morbidity i.e. seizure, developmental
delay or paralysis. Japanese B encephalitis vaccine is mandatory in Thailand. Current vaccine used in our institution consists of 2 doses of live-attenuated vaccine given 3-12
months apart.