One of the great success stories of medicine has been the conquest of seven major childhood diseases - whooping cough, measles, rubella, mumps, diphtheria, tetanus, polio - a feat made possible by immunization. Yet this very success has produced its own dangers.

While Utah parents generally have done a decent job of getting their children immunized, the figures are declining and youngsters are being put at risk.The success of immunization programs has made a new generation of parents forget - if they ever knew - the dreaded dangers of the basic childhood diseases, particularly polio. It is an "out of sight, out of mind" situation for many, according to the state health director.

State law requires that children going to school for the first time be properly immunized, and most are. However, this past year showed that for every 10 entering school who had received all the necessary vaccines, there was one child who hadn't.

For pre-school children, the numbers are worse, with only 60 percent of 2-year-olds having the recommended immunization.

As a result of this slippage, the number of cases of pertussis, or whooping cough, has increased significantly. In 1985 and 1986 there were more cases reported than in any year since 1965.

Gov. Norman Bangerter has declared August as immunization month. The timing is right as children prepare to enter school. Some parents complain that they don't have time, but priorities can and must be shuffled for something so important. Cost is no excuse, either. State law says no child can be denied immunization at a public clinic because of the family's inability to pay.

Parents should make sure every child is up to date on his or her immunizations. The dreaded diseases of childhood have not been eliminated; they are only being held at bay. It would be inexcusable to allow them to make any kind of a comeback.