According to the Associated Press, U.S. health officials told pediatricians to temporarily quit using one of two vaccines against a leading cause of diarrhea in babies, after discovering that doses of GlaxoSmithKline''s Rotarix were contaminated with bits of an apparently benign pig virus. Glaxo''s vaccine has been used in millions of children worldwide, including 1 million in the U.S., with no signs of safety problems -- and the pig virus isn''t known to cause any kind of illness in people or animals, said Dr. Margaret Hamburg, commissioner of the Food and Drug Administration. But vaccines are supposed to be sterile, and because there is a competing vaccine against diarrhea-causing rotavirus that has tested clean — Merck''s RotaTeq — the FDA decided to err on the side of caution. Rotavirus causes severe diarrhea and is a leading child killer in developing countries. In the U.S., with better health care, about 55,000 children a year were hospitalized for rotavirus infections and several dozen died each year before vaccination began — with Merck''s vaccine in 2006 and Glaxo''s in 2008. Glaxo said that regulators abroad have decided not to change how Rotarix is used while scientists probe the relevance of the discovery.