The MMR vaccine protects your child against three viral diseases -- measles, mumps, and rubella -- all of which are spread from person to person through the air.
Measles is a highly contagious infection that causes a rash all over the body, cough, runny nose, eye irritation, and fever. If left untreated, the infection can lead to ear infections, pneumonia, seizures, brain damage, and even death. Until the MMR vaccine became available in the 1970s, nearly all children in the U.S. had measles by the time they were 15 and nearly 50,000 people were hospitalized each year.
The mumps virus is most known for its telltale chipmunk cheeks, caused by swollen glands in the jaw. Serious infections can lead to permanent hearing loss, meningitis (an infection of the lining of the brain and spinal cord), painful swelling of the testicles or ovaries and, rarely, even death. Like measles, mumps used to be a common illness in infants, children and young adults.
Rubella, also known as German Measles, is an infection that causes rash, mild fever, and arthritis. Women who get the disease while pregnant are at risk for miscarriage or having a baby with serious birth defects. Before the MMR vaccine was available, a rubella outbreak in the U.S. caused 12.5 million people to get the disease in one year -- and 20,000 babies were born with birth defects as a result.
Now, after decades of vaccination in the U.S., all three of these diseases have been all but eliminated here. Small outbreaks do still occasionally occur, mostly when unvaccinated people contract one of the diseases and spread it to others who haven't been vaccinated.