* Merck vaccine not affected
* Suspension is temporary - no evidence of harm
* Rotavirus vaccines have troubled history (Adds WHO, European regulator comment)
By Maggie Fox, Health and Science Editor
WASHINGTON, March 22 Doctors should temporarily stop using GlaxoSmithKline Plc's (GSK.L) (GSK.N) Rotarix vaccine against a diarrhea-causing virus called rotavirus because it is contaminated with an apparently harmless pig virus, regulators and the company said on Monday.
Doctors should instead give children Merck and Co Inc's (MRK.N) RotaTeq rotavirus vaccine, which is made using a different method and which shows no evidence of the virus, the U.S. Food and Drug Administration said.
The FDA and the company both found DNA from the virus in the vaccine. It is not clear whether whole virus is in the vaccine or just pieces of its DNA.
"We do believe the product is safe," FDA Commissioner Dr. Margaret Hamburg told reporters in a telephone briefing. Most children in the United States have been vaccinated with Merck's vaccine, which came onto the market sooner than Rotarix, she said.
Hamburg said the FDA was acting out of an abundance of caution. 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 called intussusception.
The contaminating virus in Rotarix, called porcine circovirus type 1 or PCV-1, is not known to cause disease.
"PCV-1 does not multiply in humans and is not known to cause illness in humans. It is found in everyday meat products and is frequently eaten with no resulting disease or illness," the company said in a statement.
The FDA said its vaccine advisory committee would meet within the next four to six weeks to review the issue.
DEATHS FROM ROTAVIRUS
The World Health Organization said the risks from rotavirus, which kills 500,000 children a year globally, outweigh and potential risks from PCV.
"WHO does not recommend any change to use of the vaccine in developing countries," the United Nations health agency said in a statement. The European Medicines Agency asked Glaxo to urgently check how the vaccine became contaminated. [ID:nLDE62L24S]
Circoviruses are tiny animal viruses. Porcine circovirus type 2 or PCV-2 is believed to cause postweaning multisystemic wasting syndrome in young piglets, marked by diarrhea and an inability to gain weight. PCV-1 is related but appears to cause no disease in pigs.
Tests in human cells showed PCV-2 could damage the cells but PCV-1 did not.
"No safety issue has been identified by external agencies or GSK. GSK is committed to patient safety and to the highest manufacturing standards for all our vaccines and medicines. We are already working closely and discussing this finding with regulatory agencies around the world," said Thomas Breuer, Glaxo's chief medical officer.
Breuer said 69 million doses of Rotarix had been distributed with no evidence of a safety problem.
Hamburg said about 1 million U.S. children have received Rotarix, which came onto the market in 2008.
The DNA from the virus was found by accident, when the company ran checks using new molecular detection techniques. The virus has apparently been there since the vaccine was first developed.
"GSK is now reviewing how best to replace, in a timely way, the cell bank and virus seeds used as base production material," the company said. It said it would continue to make Rotarix, however, using current methods.
In afternoon New York Stock Exchange trading, Merck shares were up 54 cents or 1.4 percent to $38.60, while GlaxoSmithKline shares were up 49 cents or 1.3 percent to $39.06. (Reporting by Lisa Richwine and Maggie Fox; editing by Gerald E. McCormick, Bernard Orr)