Twice-daily doses of penicillin for babies and toddlers with sickle-cell anemia can reduce dramatically the risk of life-threatening infections that kill nearly one in 10 youngsters with the disease during their first three years of life, according to a major national study released today.

The study showed that such preventive doses resulted in 84 percent fewer blood infections from a toxic bacterial organism known as Streptococcus pneumoniae.

The results were so promising that the government-sponsored study at 23 medical centers nationwide, including Children's Hospital here, was stopped after 19 months, eight months ahead of schedule. The findings are published today in the New England Journal of Medicine.

"We think this has tremendous public-health implications," Dr. Claude Lenfant, head of the federal National Heart, Lung and Blood Institute, told reporters here.

Dr. Marilyn Gaston of the institute's Sickle Cell Disease Branch said study participants recommended that all black infants and others at risk be screened at birth for sickle-cell anemia and that children found to have it be administered penicillin orally by at least four months of age.

"I hope this study will be the impetus," Dr. Roland Scott, head of the Center for Sickle Cell Disease at Howard University, said. "I would certainly endorse it. It's going to result in saving the lives of babies who otherwise might perish from infection."

Under a new city law, he said, the District government recently began offering voluntary sickle-cell screening of all hospital newborns.

Gaston said the blood test costs about $2 and that the penicillin regimen about $30 to $50 annually.

"This is the first drug to directly benefit patients with sickle-cell disease," said Dr. John Falletta, a Duke University physician who chaired the study. But, he emphasized, "It treats the complications of the disease," not "the disease itself."

Nonetheless, Gaston and Falletta said using penicillin as preventive therapy could have immediate life-saving consequences worldwide.

They estimated that as many as 30 percent of children with sickle-cell anemia are expected to develop a blood infection from pneumococcal bacteria during their first three years when they are most vulnerable. As many as one-third could die from it, the study said.

Sickle-cell anemia is one of the most common genetic disorders, afflicting about one in 400 blacks born in this country. Although rare in Caucasians, it can occur in those of Hispanic, Middle Eastern or Mediterranean origin.

Regular use of oral penicillin could help prevent most of the 150 to 180 deaths each year among an estimated 5,000 U.S. blacks under age 3 with the disease, Gaston said. Worldwide, about 600,000 children under 3 have the disease, and about 18,000 to 20,000 of them die from infections each year, she said.

Because of an abnormality in the oxygen-carrying hemoglobin molecule, inherited from both parents, red blood cells can become sickle -- shaped, rather than spherical, in victims. The deformed cells can block key organs, such as the spleen.

Falletta noted that the spleen acts as a "garbage-disposal unit" to remove circulating bacteria and assists in developing immunity to bacteria. Sickle-cell victims may begin to lose spleen function as early as 3 months of age.

The government study involved 215 children from 3 months to 36 months, half of whom were given penicillin tablets twice a day and the other half a placebo.

During the study, of 13 children in the placebo group who contracted pneumococcal infections, three died and one had a stroke that led to severe nervous-system impairment. The infections progressed rapidly from fever to death or septic shock in fewer than nine hours, Gaston said, so treatment was often too late.

In contrast, only two infections occurred among children receiving penicillin, the report said. Gaston said further study is needed to determine how long to continue penicillin therapy beyond the third birthday. The study found no major side effects from penicillin, but such potential risks also require further research, she said.