Fever of 39 degrees Celsius after playing the B brain vaccine should be taken under the guidance of a doctor to reduce fever medication such as ibuprofen, etc. After taking the medicine, the temperature is still unable to control the advice to go to the hospital in time for treatment. Brain B vaccine, also known as encephalitis B vaccine, is made from the brain B virus by cell culture, inactivation and purification. The vaccine can stimulate the body to develop immunity to the encephalitis B virus. Mild fever may occur after vaccination with EBV, which is usually a normal post-vaccination adverse reaction. However, when the body temperature exceeds 38.5 degrees Celsius, measures need to be taken to control the body temperature. When the body temperature reaches 39 degrees Celsius, it is necessary to take antipyretic drugs, such as ibuprofen, under the guidance of a doctor. If the body temperature continues to rise or has no tendency to fall, it is recommended to go to the hospital for treatment in time to avoid delay.