I don't want to put works in cies's mouth, but it possible to read the comment in a reasonable way. It is not necessarily a claim that polio isn't real, but rather that patient's signs and symptoms can overlap with other medical issues. Stefan Lanka doesn't pass my sniff test, but reference to him and to test contamination can be read as examples that these sorts of tests are not always clear.
I found the roll-outs of these vaccines only came when the numbers of sick people were already well on the decline. I think polio is likely related to use of certain --now forbidden-- pesticides.
Animal testing played a significant role in development of a Polio vaccine. I understand you are making a point that correlation is not causation, but there are actual animal trials where they purposefully infected monkeys and watched the disease progression. There are plenty of things we may not understand in the world, but we do understand some science well enough to prove beyond reasonable doubt causal relationships in certain kinds of experiment design.
