Federal officials approve a new vaccine by New Jersey-based Merck that protects infants from rotavirus. The disease causes diarrhea and dehydration and leads to hundreds of thousands of deaths a year in developing countries.

In the U.S., more than 70,000 children are hospitalized each year because of the infection.But in trials, RotaTeq prevented at least 98 percent of severe cases of gastroenteritis, or intestinal inflammation. It was tested on 60-thousand babies.

In 1999, a different rotavirus vaccine made by Wyeth, another New Jersey-based firm, was pulled from the U-S market after it was linked to a small increase in intussusception, a rare, life-threatening blockage or twisting of the intestine.

The Rotateq vaccine is expected to be recommended for all children and added to their routine list of vaccinations by the C.D.C. within the month. It will probably be in doctors offices by the first week of March.