Evidence of DNA from two pig viruses have been found in Merck & Co’s rotavirus vaccine Rotateq, but there is no evidence of a safety risk, US health officials have confirmed.

The finding follows the March findings by University of California researchers of the DNA of a porcine circovirus known as PCV1 in the vaccine.

Last week, the FDA announced that subsequent sensitive tests had found low levels of the same PCV1 virus, as well as PCV2.

Both viruses are common in pigs, but they are not known to cause illness in humans.

Similar DNA fragments have also been found in GlaxoSmithKline PLC’s Rotarix vaccine and an FDA panel is scheduled to meet to discuss further action on both vaccines.

In the meantime, the vaccines will remain on the market while additional studies are conducted.

GSK and Merck’s vaccines are designed to protect infants from a gastrointestinal illness caused by rotavirus.