Fever is a common adverse reaction after vaccination. The principles of treatment are: when the body temperature exceeds 38.5 degrees and the child is in a poor mental state and drowsy, you can give the child antipyretic medicine, Merlin or Ibuprofen orally, and also give the child more warm water and wipe the body with warm water, all of which can help lower the temperature. If the body temperature is below 38.5 degrees and the child is in good spirits, you can observe first, do not take antipyretic drugs, and take physical cooling measures, such as applying antipyretic patches, taking warm baths, and drinking more hot water. Generally, fever after vaccination appears within 24 hours of vaccination, and the temperature usually lasts 1-2 days and then recedes. If the fever lasts more than 48 hours, it is best to go to the hospital.