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I'm certainly not an expert, but you can read up on the phenomenon here if you want to. The search I did just now indicates that it's a well recognized phenomenon.
The situation is that the vaccine has a very small chance of actually creating polio in the recipient and since the disease had been nearly eliminated many current cases are from the vaccines.
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Maybe, maybe not. It sounds strange to me however: we got it almost eradicated using vaccines but now the vaccines cause its reemergence? I would say it is because of insufficient collective immunity.