The MMR vaccine can be given to children between the ages of one and a half and two weeks. The MMR vaccine is given to children to prevent measles, rubella and acute mumps. These three diseases are very dangerous for children and can cause pneumonia and encephalitis, which can seriously affect their health, so the MMR vaccine is necessary. When children are younger, the rate of adverse reactions to the vaccine increases, but when children reach the age of one and a half weeks, the rate of adverse reactions to the MMR vaccine decreases and the vaccination is more effective, preventing children from having measles, rubella and mumps.