Baby two years old after playing the B brain vaccine fever 38.7 ℃, considered to be the injection of B brain vaccine after the adverse reaction, usually 1 ~ 2 days after the self-relief, if necessary, should be physical cooling and medication to reduce temperature and other treatments. Encephalitis B vaccine is divided into live attenuated encephalitis B vaccine and freeze-dried inactivated encephalitis B vaccine (Vero cell). Both types of vaccines are associated with adverse reactions of fever. For mild febrile reaction, it can be relieved on its own after 1-2 days, and no treatment is needed. If necessary, rest appropriately, drink plenty of boiled water, pay attention to warmth, and prevent secondary infection. For moderate to severe febrile reaction or fever time more than 48 hours, can be given warm water wipe and other physical methods or use ibuprofen, acetaminophen and other drugs symptomatic treatment. To prevent hyperthermic convulsions. After vaccination, it is recommended to have a light and easy-to-digest diet, and pay attention to the baby’s temperature, mood, general condition and other changes, and consult the doctor if necessary.