The MMR vaccine, known clinically as MMR triple vaccine, is used to prevent measles, mumps, and rubella. How long it takes to be considered safe after MMR vaccination refers to how long it takes for adverse reactions associated with the vaccination to abate or subside, although there is variability among children. A small percentage of vaccinated children may experience fever and malaise within 48 hours after vaccination is completed. If the body temperature does not exceed 38.5℃, physical cooling can be carried out, and metabolism can be promoted by drinking appropriate amount of water and paying attention to appropriate amount of rest to relieve symptoms; if the fever exceeds 38.5℃, in addition to physical cooling, medication is also needed to lower the temperature, and acetaminophen and ibuprofen are commonly used clinically. In addition, a few children may develop a transient rash or localized redness, swelling, pain and fever for about 6-11 days. It is necessary to pay attention to local hygiene, keep the rash area dry, and avoid scratching and rubbing. The above symptoms will usually subside on their own in about half a month and no special treatment is needed; if the rash is serious and persistent, you need to go to the hospital in time. In addition, the protection period of the MMR vaccine is about 10 years, and the vaccination can play a good role in preventing the disease. It should be noted that the protection rate of the vaccine is not 100% and there is still a certain risk of infection. Therefore, parents should pay attention to the balanced nutritional intake of children, not to be picky about food, pay attention to dietary hygiene, and exercise moderately to strengthen resistance.