Pieces of DNA from a pig virus were found in Merck & Co Inc's vaccine against a diarrhea-causing infection, but U.S. health officials said on Thursday there was no evidence of a risk to people.
DNA from the same virus was found in a rival GlaxoSmithKline Plc vaccine. Glaxo and the Food and Drug Administration in March urged doctors to suspend use of that vaccine, but there was no similar recommendation for Merck's product.
The FDA will seek input on both vaccines, which fight rotavirus infection, at an advisory panel meeting on Friday.
Merck said the company's preliminary testing found "very low levels" of DNA from porcine circovirus, or PCV, in its Rotateq vaccine.
"There is no evidence at this time that DNA from PCV causes any disease in humans," Merck said in a statement.
The FDA said the number of virus DNA fragments in the Merck vaccine may be smaller than what has been found with Glaxo's product, called Rotarix.
"FDA has no evidence to date that these findings pertaining to Rotarix and RotaTeq pose a safety risk. Both vaccines have strong safety records, including clinical trials involving tens of thousands of patients and clinical experience with millions of patients," the agency said in a statement.
Rotavirus vaccines have a troubled history. Wyeth's Rotashield was pulled off the market in 1999 after it was linked with a rare but deadly bowel obstruction.
Merck's tests found fragments of DNA from PCV1 and a related virus called PCV2. Tests of Glaxo's vaccine found only DNA from PCV1.
Both types are common in pigs but neither is known to cause illness in humans, the FDA said. PCV2 is believed to cause postweaning multisystemic wasting syndrome in young piglets, marked by diarrhea and an inability to gain weight.
FDA spokeswoman Shelly Burgess said the agency felt it was appropriate to hear from the advisory panel as officials consider future recommendations for both vaccines.
The vaccines prevent infection with rotavirus, which can cause severe diarrhea and kills more than 500,000 infants each year, mostly in low- and middle-income countries.
When Glaxo announced the pig virus finding in March, the World Health Organization said the risks from rotavirus outweighed any potential risks from PCV. It did not recommend any change to use of the vaccine in developing countries.
Merck said it tested Rotateq for PCV after the Glaxo findings were announced in March and immediately shared results with the FDA.
"We remain confident in the safety profile and quality of Rotateq. Rotavirus vaccines are a major public health advance," the company said.
In Glaxo's case, the virus DNA was found by accident when the company ran checks using new molecular detection techniques. The virus had apparently been there since the vaccine was first developed.
Glaxo has said no safety issues were identified with Rotarix and the company is working to replace the cell bank and virus seeds used to make Rotarix.