Rotavirus vaccine nears U.S. market

WASHINGTON — A vaccine against a virus that hospitalizes thousands of children in the U.S. with diarrhea and kills millions in developing countries moved a step closer to the U.S. market on Wednesday.

If the government gives the go-ahead, Merck's vaccine would become the nation's second attempt at preventing rotavirus. A competitor's vaccine was pulled from the market six years ago because of a rare but life-threatening side effect.

Federal health advisers unanimously voted Wednesday that Merck's candidate, RotaTeq, seems safe and effective. They also urged careful monitoring to watch for that side effect, a twisted bowel condition, and other possible problems.

The members of the Food and Drug Administration's expert panel on vaccines said they were concerned about trial data that showed a few more children who took the vaccine developed seizures than did those who took a placebo. It was unclear if the vaccine played any role.

The FDA is not bound by the decisions of its advisory committees, but often follows their recommendations.

Merck officials said they would conduct a follow-up study to track any long-term effects of the vaccine, which has been in development since 1993.

In the United States, rotavirus infects many children before their third birthday and sometimes sends them to the hospital. The virus kills several dozen children annually in the U.S.; most children eventually develop an immunity.

In developing countries, where there is less medical care, rotavirus kills one child in 250.

The FDA advisers expressed some wariness about approving the vaccine after problems linked to the earlier vaccine, RotaShield. The manufacturer, Wyeth, pulled that vaccine in 1999 after 20 infants developed the bowel condition within a month of receiving the treatment. More than 1 million children were vaccinated.

Researchers in the RotaTeq trials looked closely for cases in which children developed the condition, called intussusception. They found it did not occur more often in vaccinated children than it did among those who got a placebo.

The vaccine would be given to infants as a liquid during regular vaccinations at age two months, four months and six months.

Company officials said the vaccine is meant to be effective for two years because an older child who gets rotavirus is much less vulnerable to dehydration and other severe consequences of the illness, and therefore less likely to need hospitalization.