Safety incidents
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 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 vaccine 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. In May 1955, the National Institutes of Health and Public Health Services established a Technical Committee on Poliomyelitis Vaccine to test and review all polio vaccine lots and advise the Public Health Service as to which lots should be released for public use. These incidents reduced public confidence in polio vaccine, leading to a drop in vaccination rates.[77]
https://en.wikipedia.org/wiki/Polio_vaccine
Maybe if this person understands why it happened, and why it couldn't happen again, it would help with his understanding and confidence in modern vaccine science.
My dad had a polio scare but it was before the vaccine was invented.
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