The third dose of the vaccine is the third dose of the new crown vaccine, and adults with a high fever of 39 ℃ after vaccination, such as vaccine immune response, need to actively cool down the temperature, such as caused by other diseases need to be treated for the cause of the disease. After the new crown vaccination mostly caused by low fever, 39 ℃ high fever is rare, need to consider other causes of fever, and actively seek medical attention to find the cause of the disease. 1. Physical therapy: Physical therapy for high fever can use warm water to apply external compresses on the body surface, such as armpits, thigh roots, neck, etc., to reasonably reduce the body surface temperature. Drink some water to adjust the internal environment, reasonable urination and sweating to reduce temperature. 2. Drugs to reduce fever: body temperature over 38.5 ℃, can be given under the guidance of the doctor antipyretic drugs, such as acetaminophen, ibuprofen suspension. 3. Etiological treatment: patients with bacterial infection can be treated with antibiotics such as cefixime granules, penicillin V potassium tablets, cephradine tablets, etc. under the guidance of professional doctors. Viral infections can be treated with antiviral drugs such as ribavirin. If you have a high fever after vaccination, it is recommended that you consult a doctor in time to clarify the cause and then follow the doctor’s instructions to carry out the appropriate treatment. Avoid self-medication to avoid delaying the condition.