Poliovirus vaccine contamination prompts cancer fears.

Presents the results of an epidemiological study which reveal that simian virus 40 contamination of poliovirus vaccine may have occurred in the former Soviet Union after 1963. Reference to a study by Michele Carbone that was presented at the Vaccine Cell Substrate Conference 2004 in Rockville, Maryland; Concern that a significant number of people may have been exposed to the virus than was previously thought; Clarification of Janet Butel from the Baylor University College of Medicine that the consequences are yet unclear.