In April 1955, soon after mass polio vaccination began in the US, the Surgeon General began to receive reports of patients who contracted paralytic polio about a week after being vaccinated with Salk polio vaccine from the Cutter pharmaceutical company, with the paralysis limited to the limb the vaccine was injected into. The Cutter vaccine had been used in vaccinating 200,000 children in the western and midwestern United States.[76] Later investigations showed that the Cutter vaccine had caused 40,000 cases of polio, killing 10.[76] In response the Surgeon General pulled all polio vaccines made by Cutter Laboratories from the market, but not before 250 cases of paralytic illness had occurred. Wyeth polio vaccine was also reported to have paralyzed and killed several children. It was soon discovered that some lots of Salk polio vaccine made by Cutter and Wyeth had not been properly inactivated, allowing live poliovirus into more than 100,000 doses of vaccine.