MMR refers to the MMR vaccine, which is to be administered to the outer upper arm at the attachment of the lower edge of the deltoid muscle and protects against measles, mumps and rubella. MMR belongs to a class of combined live attenuated vaccines. Under normal circumstances, MMR vaccine is administered by subcutaneous injection at the attachment of the lower edge of the deltoid muscle on the lateral side of the upper arm to stimulate the body to develop immunity against measles, mumps and rubella viruses, which can prevent measles, mumps and rubella to a certain extent. The vaccine is intended for infants and young children over 8 months of age. Common contraindications include allergy to the components of the vaccine, chronic disease exacerbation, and acute diseases. Some people may experience adverse reactions such as pain, fever, skin rash and parotid gland enlargement after vaccination. All in all, it is recommended to learn about the MMR vaccine before receiving it and actively cooperate with the doctor during the vaccination. If there are special circumstances, the vaccination should be carried out according to the doctor’s recommendation.