Before the polio vaccine, Doctors used to routinely call any childhood paralysis polio. It played well on insurance forms. Here’s an analysis of the Detroit polio epidemic of 1958. http://jama.jamanetwork.com/article.aspx?articleid=327642 They had a big epidemic, but when they went in and examined the cases, it turned out that less than 1/3 of the patients even had polio virus, and whether it is what was causing their problem is of course even then unclear. Maybe they would have beat it easy without some other factor (eg DDT).
So how did the polio vaccine stop a disease where at least 2/3 of the cases didn’t have the virus? It seems plausible that most polio cases back in the day were mostly or entirely DDT poisoning. Polio is normally a very mild disease. DDT exposure makes you more vulnerable. http://www.ncbi.nlm.nih.gov/pubmed/4285235
Supposedly rich people used to spray DDT around to keep bugs away, prevent polio. (Here's a paper arguing that FDR didn't even have polio: http://www.ncbi.nlm.nih.gov/pubmed/14562158 ) In so doing, some maybe gave their kids polio, much like parents today, thinking to protect their kids, seem to be vaccinating them and making them sick.
Here's another discussion of the history of polio. https://idsent.wordpress.com/2015/03/15/sorry-in-the-vaccine-debate-the-experts-are-the-historians/?fb_action_ids=10206904382260412&fb_action_types=og.shares
It discusses in detail how the definition of polio was changed when they introduced the vaccine, how the timing of polio epidemics suggests that they were actually caused by DDT spraying campaigns, how the early polio vaccine also caused increase in polio cases, and more about how the contamination of polio vaccine by SV-40 was discovered and ignored by authorities and covered up.