Pig virus DNA found in Merck's Rotateq vaccine

The U.S. Food and Drug Administration reported May 6 that fragments of two types of pig viruses were found in Merck & Co.'s Rotateq vaccine.

One virus is the same one found in GlaxoSmithKline PLC's Rotarix vaccine in March. The FDA, at the time, recommended doctors stop using that vaccine and use Rotateq instead, even though the agency said it didn't think the virus posed any safety risks to humans.

Both vaccines are designed to protect infants from a gastrointestinal illness caused by rotavirus and have been given to millions of babies since Merck's Rotateq vaccine was approved for use in the U.S. in 2006.

Officials said tests identified fragments of DNA from PCV1 and from a related porcine circovirus, PCV2, in its Rotateq vaccine. PCV1 and PCV2 are common in pigs. Neither PCV1 nor PCV2 are known to cause illness in humans. However, FDA officials said PCV2 may cause illness in pigs.

“We don't exactly know the source of the PCV finding in Rotateq,” Mark Feinberg, vice president, medical affairs and policy at Merck Vaccines Mark Feinberg, told Dow Jones Newswires.

One theory is that the PCV could be derived from trypsin, an enzyme derived from pigs that's used in the manufacturing process. The findings raise questions about whether PCV fragments might be found in other vaccines on the market as well as those in development.

The safety of both Rotateq and Rotarix has been tracked by the FDA since another vaccine by then drug maker Wyeth was pulled off the market in 1999. That vaccine was linked to an increased rate of intussusception, which is a twisting or obstruction of the intestine that can be fatal.

In 2007, the FDA issued a public health notice saying it had received 28 reports of intussusception linked to Rotateq. At the time, the FDA said the intussusception rate wasn't higher than the rate that would be expected to occur among non-vaccinated infants. Later that year the Centers for Disease Control and Prevention also said there was no increased risk of intussusception from Rotateq.
The FDA said it will not make any final decisions regarding the rotavirus vaccines until after a May 7 advisory panel meeting.