Cessation of use of trivalent oral polio vaccine and introduction of inactivated poliovirus vaccine worldwide, 2016

Since the 1988 World Health Assembly resolution to eradicate poliomyelitis, transmission of the 3 types of wild poliovirus (WPV) has been greatly reduced. WPV type 2 (WPV2) has not been detected since 1999 and was declared eradicated in September 2015. Given that WPV type 3 has not been detected since November 2012, WPV type 1 (WPV1) is likely to be the sole WPV remaining in circulation. This marked progress has been achieved through widespread use of oral poliovirus vaccines (OPVs), most commonly trivalent OPV (tOPV), which contains types 1, 2 and 3 live, attenuated polioviruses, and has been a mainstay of efforts to prevent polio since the early 1960s. Attenuated polioviruses in OPV can undergo genetic changes during replication, and in communities with low vaccination coverage rarely result in vaccine-derived polioviruses (VDPVs) that can cause paralytic polio indistinguishable from the disease caused by WPVs.