Admittedly, Salk's vaccine logged early success; some 60-70 percent of those vaccinated did not develop the disease. But it also saw some early problems. About 200 people who had been vaccinated got the disease, and 11 of them died, forcing a halt to all testing. Once it was determined that a faulty, poorly manufactured batch of the vaccine was the cause of those cases, stricter production standards were implemented and full-scale vaccinations nationwide resumed once more. Four million vaccines were given by 1955; by 1959, 90 countries were using it.
That said, those early cases were far from the last time the vaccine killed. In fact, throughout its history of use, Salk's polio vaccine left a path of death its wake.
Dr. Eddy discovered that the cells would die without any apparent cause. She then took suspensions of the cellular material from these kidney cell cultures and injected them into hamsters. Cancers grew in the hamsters. Shortly thereafter, scientists at the pharmaceutical company Merck & Co. discovered what would later be determined to be the same virus identified by Eddy. This virus was named Simian Virus 40 or SV40 because it was the 40th simian virus found in monkey kidney cells.
