Modeling the potential role of inactivated poliovirus vaccine to manage the risks of oral poliovirus vaccine cessation.

Abstract

The Global Polio Eradication Initiative plans to stop all oral poliovirus vaccine (OPV) after wild poliovirus eradication, starting with serotype 2. Stakeholders continue to discuss the role of using inactivated poliovirus vaccine (IPV) to manage the risks of circulating vaccine-derived polioviruses (cVDPVs) during the end game. We use a poliovirus transmission and OPV evolution model to explore the impact of various routine immunization policies involving IPV on population immunity dynamics and the probability and magnitude of cVDPV emergences following OPV cessation. Adding a single IPV dose to an OPV-only routine immunization schedule at or just before OPV cessation produces very limited impact on the probability of cVDPV emergences and the number of expected polio cases in settings in which we expect cVDPVs in the absence of IPV use. The highest-cost option of switching to a 3-dose IPV schedule only marginally decreases cVDPV risks. Discontinuing supplemental immunization activities while introducing IPV prior to OPV cessation leads to an increase in cVDPV risks. Introducing a dose of IPV in countries currently using OPV only for routine immunization offers protection from paralysis to successfully vaccinated recipients, but it does little to protect high-risk populations from cVDPV risks.