Fever of 39℃ after MMR vaccination can be lowered by taking antipyretic medication (e.g. ibuprofen), but because each child’s physical condition is different, the dosage of the medication taken is also different, parents should not use the medication without authorization, and it needs to be done under the guidance of a physician or pharmacist. The MMR vaccine is used to prevent three infectious diseases, measles, mumps and rubella, and is usually administered to infants 8 months after birth. Some infants may have adverse reactions such as swollen lymph nodes and mild fever 7 to 12 days after vaccination. However, a fever of 39 degrees Celsius already belongs to the category of high fever, and if physical cooling no longer has a significant effect, it may be necessary to rely on the action of antipyretic drugs. If the temperature of 39 degrees or more persists for 24 hours and is still not relieved, parents should take their children to the hospital as soon as possible to inform the doctor of the exact time of the child’s vaccination, which is conducive to the doctor’s judgment of the child’s condition and the rational use of medication.