Fever usually develops within 24 hours after the B vaccine, although not all children will develop fever. Parents do not need to worry too much about the adverse effects of the vaccine, such as fever, which may occur after the vaccination. Fever symptoms in children are usually low-grade and can be handled by physical cooling therapies, such as ice packs on the forehead and warm water wipes. If the temperature is higher than 38.5℃, antipyretic drugs can be used as prescribed by the doctor. The time for fever symptoms caused by vaccination will usually be relieved within 2-3 days. If the fever persists after 3 days, it is necessary to take the child to a regular hospital for examination and treatment. In addition, there are certain contraindications to the vaccination of encephalitis B. It is recommended that parents need to consult a specialist before vaccination to find out whether their child is suitable for the vaccination, and to observe whether there are any adverse reactions after the vaccination; if the adverse reactions are more serious or continue to be unrelieved, it is necessary to consult a doctor in a timely manner.