You were alive in the 50s??? I thought you were a lot younger than that.
In any event, I'm almost positive it was a different vaccine way back then.
Here's an article from a few years ago about "vaccine-derived polio" in poor countries that still use that particular vaccine that has a live but weakened version of the polio virus. I added the bold, and the link is below the excerpt.
The oral vaccine contains a live but weakened version of the polio virus. The virus replicates inside the child's intestine and eventually is excreted. In places with poor sanitation, fecal matter can enter the drinking water supply, and the virus is able to start spreading from person to person. That was once considered a useful feature of the oral vaccine, since it can help unvaccinated children become immune. However, in rare cases in places with poor sanitation and large numbers of unvaccinated children, the attenuated virus can mutate in the wild and regain strength to the point where it can cause paralysis.
In the U.S. and other wealthier nations, children receive a polio vaccine injection that contains inactivated virus.
"It's actually an interesting conundrum. The very tool you are using for [polio] eradication is causing the problem," Raul Andino, a professor of microbiology at the University of California, San Francisco, told NPR in 2017.
