(Dow Jones)--A Food and Drug Administration panel said Friday fragments of pig viruses found in vaccines used to protect infants against rotavirus didn't appear to cause health risks.
While the panel didn't take a vote on the products, several members of the agency's vaccine panel said the vaccines -- Merck & Co.'s (MRK) Rotateq and GlaxoSmithKline PLC's (GSK, GSK.LN) Rotarix -- should remain on the U.S. market while additional studies are conducted about the impact of pig viruses.
In the meantime, the panel said parents who are considering whether to vaccinate their infants need to be informed about the findings.
FDA panels are made up of non-FDA medical experts and are called upon to make nonbinding recommendations to the agency.
Karen Midthun, acting director of FDA's Center for Biologics and Research, said the agency would be "very expeditious" in making recommendations about whether either vaccine should be used. n March, the FDA recommended that doctors stop using Glaxo's vaccine after a team of researchers from the University of California in San Francisco found DNA of a porcine circovirus known as PCV1 in the vaccine. Those tests didn't find the same pig virus in Merck's Rotateq.
However, on Thursday the FDA said more sensitive tests subsequently conducted on Rotateq found a "low level" of the same PCV1 virus, as well as a related porcine circovirus known as PCV2. Both viruses are common in pigs -- and neither is known to cause illness in humans -- but PCV2 may cause illness in pigs.
The FDA said it wouldn't decide whether it would recommend that use of Merck's Rotateq be suspended or whether it would lift its suspension recommendation involving Glaxo's Rotarix in advance of the meeting. The panel meeting had originally scheduled to discuss Rotarix but also included Rotateq in light of similar findings about pig virus fragments discovered in the product.
"PCV is not infectious in humans," said Harry Greenberg, a panel member and medical professor at Stanford University. "The benefits far outweigh the risks."
Both the Glaxo and Merck vaccines are designed to protect infants from a gastrointestinal illness caused by rotavirus and have been given to millions of babies. While rotavirus is rarely fatal in the U.S., it contributed to about 70,000 infant hospitalizations annually before Merck's vaccine was approved in 2006 and Glaxo's in 2008.
Umesh Parashar, an epidemiologist at the Centers for Disease Control and Prevention, said the most recent agency data looking at the impact of the vaccines in the U.S. show "almost...a complete wipeout of rotavirus activity." Parashar deemed rotavirus "a major killer" of children in parts of the world that can't adequately treat dehydration from severe diarrhea.
One theory about how pig virus fragments got into the vaccine offered by both the FDA and the companies is that PCV fragments might be in trypsin, an enzyme derived from pigs that is used in the manufacturing process of the vaccine. The enzyme is used to grow viruses used in the vaccines.
Barbara Howe, a GlaxoSmithKline vice president in the company's vaccine division said, "all available data support PCV1 in Rotarix is a manufacturing quality issue, not a safety issue." She said the company is working on ways to remove PCV from the vaccine but that developing a new manufacturing process "is complex and will take time."