Ever consider that polio was nearly eradicated because it was generally poorly defined prior to 1955 and over-diagnosed (often noted to be “flu-like symptoms”) and/or possibly because the diagnosis was made much more stringent after 1955 (literally the same year the vaccine was introduced)?
“The original diagnostic criteria for polio came from the World Health Organization and included:
“Signs and symptoms of nonparalytic poliomyelitis with the addition of partial or complete paralysis of one or more muscle groups, detected on two examinations at least 24 hours apart.”
It changed in 1955 to include residual paralysis 10 to 20 days after onset of illness and again 50 to 70 days after onset.”
https://vaxopedia.org/2018/07/25/th...ecause-they-changed-the-way-it-was-diagnosed/
After this diagnostic change was made, ~99% of cases would be eliminated because nearly all polio cases resolve on their own.
“Non-paralytic aseptic meningitis occurs in 1% to 5% of polio infections in children. The clinical presentation includes stiffness of the neck, back, or legs, usually following several days of a prodrome similar to that of minor illness. Increased or abnormal sensations (e.g., pain in the limbs, back, or neck), headache, and vomiting can also occur.
Typically, symptoms last 2 to 10 days and are followed by complete recovery.
Less than 1% of all polio infections in children result in flaccid paralysis.
https://www.cdc.gov/vaccines/pubs/pinkbook/polio.html