The MMR vaccine usually passes its safety period in about 7 days. MMR vaccination is mainly for the prevention of measles, rubella and mumps. Some children may have some adverse reactions after receiving the MMR vaccine, such as localized redness, swelling, pain, fever, malaise or transient rash, etc. Usually these symptoms can be gradually reduced or subsided in about 7 days. The specific days of MMR vaccine through the safety period is mainly related to the individual constitution of children, and there are individual differences. Adverse reactions to MMR vaccination usually do not require treatment and can be observed. If there is obvious fever or the rash is serious, it is recommended to go to the hospital as soon as possible.