MMR vaccine is a combined live attenuated vaccine that protects against three infectious diseases: measles, rubella and mumps. The vaccine stimulates the body to produce antibodies to the measles, rubella and mumps viruses. Measles, mumps and rubella are all acute respiratory infections caused by viruses that spread through the respiratory tract via airborne droplets. Children and adolescents are at high risk and a collective outbreak can have serious consequences. Some vaccinated persons will have adverse reactions after receiving MMR vaccine, usually fever or pain at the injection site, etc., about 24 hours after vaccination, which in most cases will disappear naturally within 2 to 3 days. For those who are suffering from acute diseases, allergy, fever, etc., vaccination is not recommended. To sum up, MMR is a vaccine to prevent measles, mumps and rubella, but the specific vaccination matters need to go to the local CDC, and be guided by professional staff according to the actual situation of the children to be vaccinated.