There have been no new cases of naturally occurring polio in North America in recent years  Yet there are approximately 12 new cases of polio each year in North America, all caused by the commonly administered live oral polio vaccine (OPV)  Substituting inactivated polio vaccine (IPV) for most childhood polio immunizations would cut the number of cases of vaccination-caused polio about in half
Clearly it is time to switch from OPV to IPV as the most commonly used polio vaccine for North American children
If IPV replaces OPV as the most commonly used polio vaccine, at least a few new cases of naturally occurring polio in North America will result each year.