The MMR vaccine is a combination of the measles, mumps, and rubella vaccines, and after a full course of vaccination, the positive conversion rate can reach 98% for measles, 96.1% for mumps, and 99.3% for rubella. Measles, rubella, and mumps are common infectious diseases in children, which are spread by airborne droplets, and children have no natural immunity to measles, rubella, or mumps, and are easily infected.