The Food and Drug Administration on Monday warned doctors and parents against using the Rotarix rotavirus vaccine until further testing can confirm that it is safe.

The warning follows an academic research group's discovery -- subsequently confirmed by the FDA and Rotarix manufacturer GlaxoSmithKline -- that the vaccine contains a pig virus called porcine circovirus 1, or PCV1. The virus is not known to cause illness in humans, and no adverse effects have been observed in children vaccinated with Rotarix, but the agency decided to err on the side of caution with the warning until more information can be obtained.

For the time being, the agency recommends that pediatricians use a competing vaccine, RotaTeq, manufactured by Merck. Preliminary tests have found no traces of PCV1 in this vaccine.

Rotavirus causes severe diarrhea and dehydration and is thought to cause more than 500,000 deaths in infants worldwide each year, primarily in low- and middle-income countries. Before the introduction of RotaTeq in the U.S. in 2006, the disease caused an estimated 50,000 hospitalizations and several dozen deaths each year. Rotarix was introduced in 2008. Most U.S. children who have been vaccinated against rotavirus as part of their normal vaccinations have received RotaTeq, the FDA said. About 1 million have received Rotarix.

The agency is now attempting to determine whether the vaccine contains intact PCV1 or simply viral fragments, as well as how it got into the vaccine. The agency said it will convene an expert advisory panel in four to six weeks to make further recommendations.

The World Health Organization and the European Medicines Agency are not expected to change current guidelines for using the drug, arguing that the benefit from the vaccine far outweighs any potential risk, according to a statement by GlaxoSmithKline.

An estimated 69 million doses of the vaccine have been administered globally. Worldwide sales of the vaccine in 2009 were $425 million, the company said, with $115 million in the U.S.

Many pediatricians have switched to Rotarix because it requires only two oral doses, compared with three for RotaTeq. [link to www.latimes.com]