Live attenuated encephalitis B vaccine is used to prevent epidemic encephalitis B virus infection. Epidemic encephalitis B is a contagious disease, most common in children, infection easily leads to central nervous system symptoms, and a small number of patients will have sequelae, injection of live attenuated encephalitis B vaccine is an effective way to prevent encephalitis B. The live attenuated encephalitis B vaccine belongs to the first class of the national vaccine. The live attenuated B encephalitis vaccine belongs to the national class I vaccine, and it is recommended that healthy children over 8 months of age be vaccinated with the live attenuated B encephalitis vaccine. Vaccination with live attenuated encephalitis B vaccine can stimulate the body to produce antibodies against encephalitis B virus, thus achieving the effect of preventing epidemic encephalitis B. For children who are frail and sickly, the vaccine is effective in preventing encephalitis B. Vaccination is not recommended for infirm children, children with a history of epilepsy, and children with acute illnesses.