A fundamental complexity of polio eradication is that the elimination of wild poliovirus (WPV) alters the risk-benefit profile of using oral polio vaccine (OPV)---as WPV is eliminated, OPV produces an increasing proportion of the paralytic disease burden since, in rare instances, OPV causes paralysis in vaccine recipients and generates circulating vaccine-derived polio outbreaks (cVDPV) in under-immunized populations. Therefore, to secure the success and long-term stability of polio eradication after the elimination of WPV, OPV use should eventually cease. Type 2 OPV (OPV2) was withdrawn from routine immunization (RI) in April 2016, but detection of type 2 cVDPV has necessitated the use of OPV2 in outbreak response. Thus the world today: RI with OPV2 has stopped, but OPV2 is needed to interrupt outbreaks, and any future OPV2 use several years hence will take place in a population with an unprecedented lack of type 2 immunity. To better understand the complex risk landscape of OPV cessation, we reproducibly summarized data spanning 75 years of polio literature detailing how vaccination affects individual-level susceptibility to infection and viral shedding. We then examined individual-level immunity in the context of close-contact transmission data from the USA and India to quantify the impacts of vaccination on transmission. Our results demonstrate that in settings with inadequate sanitation: (1) OPV has been effective in all populations because it blocks transmission locally, (2) cross-immunity against type 2 produced by bivalent OPV is insufficient to block OPV2 transmission, (3) IPV boosting after prior OPV or WPV exposure is effective for interrupting transmission in settings where inadequate or waning immunity permits significant re-infection, and (4) OPV transmission is limited more by population immunity than attenuation and so the risk of seeding new cVDPV with OPV use will increase substantially a few years after OPV cessation. We conclude with discussion of the implications for policy decisions about IPV and OPV use and vaccine research.