You may wonder why your child must be immunized against rubella before entering school in Iowa -- isn't rubella that mild disease commonly known as "three day measles"?

Yes, rubella is usually a mild disease in adults and children, possibly appearing only as a rash or slight fever.

But for unborn children, the disease can be devastating, says Dr. Betty Edmond, a pediatrics infectious diseases specialist in the University of Iowa College of Medicine.

"A fetus that has been exposed to rubella may be born with heart, or eye damage or brain abnormalities," Edmond says. "It's primarily to protect the fetus that we immunize a large part of the populace."

Immunization of school-age children is holding down the number of cases of rubella and , as a result, it is much less likely that a pregnant woman will be exposed to the disease.

During a major rubella epidemic in 1964 before the development of the rubella vaccine, about 300,000 cases of congenital (acquired before birth) rubella were reported in the United States, Edmond says.

"But since the advent of the vaccine in 1969, there have been fewer than 200 cases reported in the country."

Iowa law exempts girls 12 years and older from rubella immunization because they often already are of child-bearing age. As the rubella vaccine is a mild form of live virus, it can infect a fetus.

A comparison with Great Britain dramatizes the effectiveness of the vaccination requirements of Iowa and other states. Edmond notes that the British do not require immunization against rubella before the age of puberty (age 10 to 14). As a result, congenital rubella cases in Britain still occur about the same rate as before the vaccine was developed.