From the Wikipedia page for poliomyelitis eradication:
A study carried out in an isolated Eskimo village showed that antibodies produced from subclinical wild virus infection persisted for at least 40 years. Because the immune response to oral polio vaccine is very similar to natural polio infection, it is expected that oral polio vaccination provides similar lifelong immunity to the virus.
What studies support the notion that oral polio vaccine provides a lifelong immunity similar to subclinical wild virus infection? The quote from Wikipedia gives only inference.