PRINCE GEORGE, British Columbia -- Andrew Knickle found something he hardly expected - or wanted - after he haggled down the price of a box of sailing tarpaulins to $2.50 at a yard sale. "It was a kind of a hard, plastic tube with a screw cap that was labeled smallpox vaccine," Knickle said. "It scared me. All kinds of things went through my head, wondering if this could be meant for some evil purpose in this day and age of bioterrorism." When he shook the package, which bore a label from Connaught Laboratories in Willowdale, Ontario, and an expiration...