Jonas Salk's polio vaccine is regarded as a veritbale medical miracle, for it largely eradicated one of the most feared diseases of the 20th century. But the story of the vaccine has a dark side, one that has never been fully told before. Between 1954 and 1963, close to 98 million Americans received polio vaccinations contaminated with a carcinogenic monkey virus, now known as SV40. The government downplayed the incident, and it was generally accepted...