Abstract
Withdrawal of type 2 oral poliovirus vaccine (OPV) in OPV-using countries required regulatory approval for use of inactivated poliovirus vaccine and bivalent OPV in routine immunization. Worldwide, a variety of mechanisms were used by member states, with some differences in approach observed between inactivated poliovirus vaccine and bivalent OPV. These included acceptance for use of World Health Organization (WHO) prequalified vaccines, registration and licensure pathways, participation in WHO-convened joint reviews of licensing dossiers, as well as pragmatic application of alternatively available mechanisms, when appropriate. Simple but effective tools were used to monitor progress and to record, authenticate, and share information. Essential to achievement of regulatory targets was ongoing communication with key stakeholders, including switch-country national regulatory authorities, vaccine manufacturers, partner organizations, and relevant units within WHO. Understanding of the regulatory environment gained through the OPV switch can be helpful in supporting further stages of the polio end game and other time-sensitive vaccine introduction programs.