Babies under 2 and adults get much sicker with measles than do elementary school children. The MMR vaccine is given in two doses, at 12 to 15 months and again between 4 and 6 years or before junior high or middle school. Most children have no side effects from the MMR vaccine, but about 5 to 15 percent develop a fever. A few develop a measles-like rash, swelling of the lymph glands, and mild pain in the joints. Mumps is known for causing painful, swollen salivary glands under the jaw, as well as fever and headache.
Mumps can be a very serious disease, causing meningitis or hearing loss.
Teenage and adult males who get mumps may have painful swelling of the testicles for several days, although no infertility problems later. They get much sicker and suffer longer than children do with the disease. Rubella is also called German measles. It's a mild disease in children, but rubella endangers the fetus when a pregnant woman catches it. As many as half of the women who contract rubella while pregnant, especially during the first three months, miscarry or deliver babies with heart disease, blindness, hearing loss, or learning problems.