The measles, mumps, and rubella vaccines are all attenuated, live-virus vaccines. This means that the virus in the vaccine is weakened but alive and theoretically can give the actual disease to the recipient. This happens very rarely, and when it occurs, the illness is usually milder than when the person is exposed to the wild virus.
While there are three separate vaccines for measles, mumps, and rubella, the most common form of the vaccine given is known as the MMR vaccine, which combines all three vaccines into one dose. The primary benefit of the combination vaccine is receiving one shot instead of three separate shots. As of January
2009, the manufacturer of these vaccines has stopped production and sales of the single component measles, mumps, and rubella vaccines and will only be producing the combined MMR vaccine. Thus, after the current stocks of the single component vaccines have been used up, it will no longer be possible to divide the MMR vaccine into three separate injections.
The MMR vaccine is recommended for all children at age one year, and a booster dose is recommended at age four to six years, usually just before entering kindergarten. If children between six and twelve months of age are traveling to an area of the world with an increased rate of measles, they should receive either the measles vaccine alone, or the MMR combination vaccine, in order to give them some protection while traveling. However, this dose will not count as one of the two doses of measles that is required for school or college; only doses after twelve months of age count for those requirements.