I agree the rates of infection seem different, but a couple points to consider:

1.) Diagnosis today is different than the 40s and 50s. They tended to diagnose by symptoms and there is a thought that more than one issue may have been blanketed by the poliomyelitis diagnosis. This was not helped by government funds being made available for children crippled by a poliomyelitis diagnosis.

2.) There is serious evidence going back to the 50s that doctors recognized by 1954 that the polio epidemic may have been iatrogenic, caused by the widespread tonsillectomy rate. There was an over-90% tonsillectomy rate and those who had complications nearly always were missing their tonsils. It's been since learned that the tonsils produce a natural serum that guards against poliovirus infection. Just this realization alone would change the rate of infection for complicated enterovirus.

3.) Some of the original epidemic may also have been caused by people being sprayed down with DDT, which has similar effects on the nervous system as polio. This would significantly effect our polio data if not all polio was polio. Story

Hence why I'm not sure polio eradication is a vaccine success story.