https://www.smokershistory.com/kirschst.htm

…the early polio vaccines were one of the government’s most notorious screwups. The vaccines were contaminated with SV40, a polyoma virus infectious to humans, and millions of people were exposed via the contaminated vaccines.

In 1954, an effort was underway to produce large quantities of a vaccine to prevent polio, a disease commonly known as polio. Dr. Bernice Eddy was invited to direct testing of the Salk polio vaccine, which used injections of inactive polioviruses to immunize people against the disease. While testing the vaccine, Eddy found that it caused paralysis in some monkeys. These monkeys, she proved, had been infected by active forms of poliovirus, indicating that the vaccine was contaminated and would cause, rather than prevent, polio in those who received it. Her discovery prompted researchers to reformulate the vaccine before its official release. But Eddy’s discovery proved an embarrassment to many scientists working on…