Cutter Incident

Catastrophic pharmaceutical manufacturing failure in April 1955 at Cutter Laboratories in Berkeley, California, where improper inactivation procedures resulted in the distribution of polio vaccines containing live poliovirus, causing 40,000 cases of polio infection, 200 cases of paralysis, and 10 deaths among vaccine recipients and their contacts.

The incident occurred during the initial rollout of Jonas Salk’s polio vaccine, which required complete inactivation of poliovirus using formaldehyde treatment. Cutter Laboratories, one of six companies licensed to produce the vaccine, failed to follow proper inactivation protocols, allowing live virus to remain in several vaccine lots that were distributed to children across western states.

Within days of the vaccine’s administration, reports began emerging of children developing polio symptoms, with the highest infection rates occurring among recipients of Cutter-produced vaccine lots. Investigation revealed that the company’s manufacturing process had not achieved complete viral inactivation, creating vaccines that actually caused the disease they were intended to prevent.

The Cutter Incident prompted immediate suspension of the entire polio vaccination program while federal investigators examined manufacturing procedures at all licensed facilities. The crisis led to the establishment of stricter vaccine safety regulations, enhanced oversight of pharmaceutical manufacturing, and the creation of more rigorous testing requirements for viral inactivation.

This documented vaccine safety failure is frequently cited in contemporary vaccine skepticism arguments, though public health officials note that the incident led to significant improvements in vaccine safety protocols and that modern manufacturing and testing procedures prevent similar failures. The Cutter Incident ultimately contributed to strengthening rather than undermining vaccine safety infrastructure.