Fever in children after vaccination may be a reaction after vaccination, which usually heals itself in 1-2 days; it may also be a secondary viral or bacterial infection, which requires seeking help from a physician and not waiting for it to heal itself. The following two cases are common in children with fever after vaccination: 1. If the body temperature is between 37.5℃ and 38.5℃ and the fever is repeated for no more than 24 hours, it is mostly a normal reaction after vaccination, and the child only needs to drink more warm water and do physical cooling, and it can usually heal itself in 1-2 days. 2. The reason is that after vaccination, the child’s body will have an immune response and resistance will be temporarily reduced, making it easy for secondary infections to occur. In this case, the child should be seen by a pediatrician and treated under the guidance of a physician, and should not be delayed. When visiting the hospital, try to give a clear account of the vaccination history, including the name and time of the vaccination, the start of the fever, and the maximum temperature, so that the physician can judge and deal with the condition.