The 1955 polio-vaccine manufacturing failure that caused paralysis cases after contaminated doses were distributed was the Cutter incident.
Cutter Laboratories produced inactivated poliovirus vaccine developed from Jonas Salk’s work. In some batches, the formaldehyde treatment failed to completely inactivate virus, so live poliovirus remained in doses that were supposed to be safe.
The vaccine was distributed in the United States and Canada. Some recipients developed paralytic polio, and infections also occurred among close contacts. Authorities halted use and investigated production, testing, and regulatory oversight.
The incident did not show that all polio vaccines were defective. It was a manufacturing failure involving particular lots. The response led to tighter testing and helped establish more rigorous federal supervision of vaccine production.