Here is a
link to a review of Paul Offit's book on the early days of the polio vaccine. "Three larger companies produced safe polio vaccines according to Salk's protocol for inactivating the virus with formaldehyde. The lack of experience and expertise at Cutter Laboratories, undetected by the inspectors, caused the disaster." Here is a
link to a biographical sketch of Bernice Eddy. "Amidst the scientific and bureaucratic chaos, Workman never told the licensing committee, and the Cutter vaccine was approved and shipped out...Eddy continued her ground-breaking research. In 1956, she worked with Dr. Sarah Stewart of the National Cancer Institute, and they identified the SE (Stewart-Eddy) polyoma virus, which can cause tumors. Eddy also identified the simian virus 40." Given that he knows the history, I am now inclined to give greater weight to things Paul Offit says.