A new oral rotavirus vaccine that protects 98 percent of infants against severe diarrhea should be added to the schedule of immunizations for babies and young children, U.S. advisers said on Tuesday.

But it must be given in infancy, when babies are the least susceptible to a rare but sometimes fatal complication of the bowels, the panel said.

The Advisory Committee on Immunization Practices, which advises the Centers for Disease Control and Prevention, voted unanimously after hearing from researchers who tested the vaccine.

They said Merck and Co.‘s Rotateq vaccine, licensed earlier this month by the U.S. Food and Drug Administration, does not cause the same problems seen in an earlier vaccine withdrawn from the market in 1999.

Rotavirus is the leading cause of severe diarrhea in infants and young children and kills 500,000 young children a year globally. In the United States it affects 2.7 million children in an average year and 75 percent of children get diarrhea from rotavirus by the time they are 5 years old.

“People assume it is a more severe disease in the developing world. It is not,” said Dr. Paul Offitt, a vaccine expert and pediatrician at Children’s Hospital in Philadelphia, whose work helped in the development of the vaccine.

“One out of five children, regardless of where you are, will have severe disease in the first five years of life. Here we can put in IVs (intravenous lines). We keep children from dying in this country because we have the resources, but the diseases is severe everywhere.”

Rotavirus puts between 55,000 and 70,000 children into the hospital in the United States each year and kills between 20 and 60 very young children.

The U.S. Food and Drug Administration licensed Merck’s Rotateq on February 3 for use in U.S. infants. It prevented any kind of rotavirus disease in 74 percent of babies tested and prevented the most severe illness in 98 percent.

During the testing, Rotateq was not seen to cause any severe events, including intussusception, a rare type of bowel obstruction. Wyeth’s rotavirus vaccine was withdrawn because it apparently raised the risk of this complication.

The Merck vaccine is not given by needle but squeezed out of a tube into the infant’s mouth. Three doses are given between 6 weeks and 8 months of age.

Analysts forecast peak annual sales of Rotateq will top $500 million.

GlaxoSmithKline Plc is expected to seek a license for a rival rotavirus vaccine, called Rotarix, later this year. Rotarix may be more potent and may require only two oral doses one or two months apart.

Rotarix was approved last summer in Mexico.

The ACIP also discussed a vaccine that prevents a sexually transmitted wart infection linked to cervical cancer but did not vote on it. On Wednesday, it will discuss broadening the recommendations on who should get the influenza vaccine.