Members of a Food and Drug Administration advisory committee meeting Friday urged physicians to continue using both commercial rotavirus vaccines despite evidence that both carry trace contaminants from a harmless pig virus. The panel did not take a formal vote on a recommendation, but a majority of participants said they thought the benefits of the vaccine far outweigh any potential risk. An agency spokeswoman said it would make no immediate recommendation on the vaccines, but would act expeditiously to come to a decision.
The FDA had recommended in March that physicians stop using one of the vaccines, trade-named Rotarix, because of the contamination, but said then that it had not found the contaminant in the second vaccine, called Rotateq. But the panel was told Friday that newer, more sensitive tests had detected minute amounts of two viruses, called porcine circovirus 1 and 2 (PCV1 and PCV2), in Rotateq. PCV1 was also found in Rotarix. Neither virus is known to infect or cause illness in humans, and no adverse effects have been observed in children who have received either of the vaccines.
Rotavirus causes severe diarrhea and dehydration and is thought to cause more than 500,000 deaths each year in infants globally. Before the introduction of Rotateq in the U.S. in 2006, the virus caused an estimated 50,000 infant hospitalizations each year. Epidemiologist Umesh Parashar of the Centers for Disease Control and Prevention told the panelists that the vaccines have produced almost "a complete wipeout" of rotavirus infections in this country.
It is not known how the pig virus got into the vaccines, but the FDA and the companies that make the vaccines speculate that it was a contaminant of the pig enzyme trypsin, which is used in manufacturing the vaccine.
Experts agreed that the contaminant is only present in minute quantities -- quantities so small, in fact, that it could not be found with tests used when the vaccines were licensed. It has only been the development of new techniques for identifying extremely small traces of DNA that has allowed researchers to find its footprints.
-- Thomas H. Maugh II