A child’s fever after a quadrivalent flu vaccine may be an adverse reaction to the vaccine and can be gradually relieved by warm water wipes and other methods. In addition, if the child has fever for a longer period of time and it does not ease, or if the temperature rises, accompanied by poor spirit, nasal congestion, runny nose and other symptoms, the child should go to the hospital promptly, which may be caused by other reasons, such as co-infection, etc., and need to be treated promptly for the cause, so as to avoid high fever convulsions and other adverse symptoms. 1, adverse reactions to vaccines: vaccines can stimulate the body’s immune response, which can lead to fever after the quadrivalent flu vaccine. However, at this time, the fever is mostly low, and there may be slight headache, malaise and other uncomfortable symptoms. At this time, you can temporarily observe and monitor the change of body temperature, wipe the child’s body with warm water, and instruct him/her to drink more water, not to take a bath for a short period of time, avoid intake of fish, shrimp, chili peppers and other stimulating foods, maintain a light diet and adequate rest, and the body temperature can gradually return to normal; 2. Co-infection: The fever may be caused by infection with bacteria, viruses and other microorganisms, resulting in an inflammatory reaction in the body, such as a cold, at this time The child may also have poor spirits, stuffy nose, runny nose, sneezing, drowsiness and other symptoms. If the body temperature exceeds 38.5℃, it is also necessary to use antipyretic drugs such as acetaminophen tablets as prescribed by the doctor to avoid febrile convulsions; 3. Disease factors: If the child has some diseases in the body that have not been cured, the quadrivalent influenza vaccine may induce the aggravation of the disease and lead to fever. There may also be symptoms of high fever, and it is necessary to clarify the cause and deal with the primary disease in time to relieve the symptoms of fever.