The History on Polio: Era 1950s

During mid-April of 1955, about 400,000 people—mostly schoolchildren—in the U.S. were vaccinated with the Salk vaccine manufactured by Cutter Laboratories. It turns out that more than 200,000 of these children, living in five western and midwestern states (Arizona, California, Idaho, Nevada and New Mexico), were injected with vaccines “in which the process of inactivating the live virus proved to be defective.” The Cutter-produced vaccines ended up causing 40,000 cases of polio. It severely paralyzed 200 children and killed 10.

Source:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1383764/

Other interesting links on polio
http://www.vaclib.org/basic/poliolymph.htm