In April 1955, Cutter Laboratories, located in Berkeley, California and one of several companies licensed by the U.S. government to produce Salk’s polio vaccine, reported a production error that resulted in the production of 120,000 doses of polio vaccine that contained live polio virus.

Within days there were reports of paralysis and within a month the first mass vaccination programme against polio had to be abandoned. Subsequent investigations revealed that the vaccine, manufactured by the California-based family firm of Cutter Laboratories, had caused 40,000 cases of polio, leaving 200 children with varying degrees of paralysis and killing 10.