All of my kids and their friends had the polio vaccine in the 60s……no problems at alll.
I don’t know why you refer to it as formerly dangerous….good lord.
.
The first tests in the 1930s were a failure, and the doctors who thought they had developed a vaccine had their careers ruined. Even in the 1950s, there were serious mistakes as the vaccines were being perfected. The “March of Dimes” campaign was going on for years to raise money to perfect a vaccine.