MMR usually refers to the MMR triple vaccination against measles, mumps and rubella. Whether it is normal to have a fever on the sixth day of MMR is determined on a case-by-case basis. If the body temperature rises below 38℃, most of them are normal and are related to the relatively low immunity of the organism after MMR vaccination. If the body temperature exceeds 38℃, accompanied by other uncomfortable symptoms, it is considered abnormal, indicating the existence of infectious lesions in the body, which requires timely medical examination and active anti-infection and cooling treatment.1. Normal phenomenon: MMR vaccine belongs to the national class of free vaccination, a kind of live attenuated vaccine, mainly for the prevention of measles, mumps and rubella three infectious diseases. The vaccination may cause mild symptoms of low fever, usually not more than a week, with a temperature of no more than 38°C, and will resolve itself within a short period of time. This is a normal post-vaccination adverse reaction and most of them do not need special treatment. 2. abnormal phenomenon: due to the temporary decrease of immune system function after MMR vaccination, it is easy to be infected by bacteria or viruses, and then fever symptoms may occur and the body temperature may exceed 38℃, which is abnormal in this case. It is necessary to go to the hospital promptly and give anti-infection treatment under the guidance of the doctor as soon as possible to help lower the body temperature quickly and relieve the discomfort. It is recommended to strengthen observation after MMR vaccination, drink more warm water, pay more attention to rest, etc., and seek medical attention as soon as possible when abnormal performance is detected.