At that time, the routine polio vaccination schedule was changed from 3 doses of trivalent OPV (which contains Sabin strain types 1, 2 and 3) to 1 dose of injectable inactivated polio vaccine (IPV) (which contains inactivated 1, 2, and 3 poliovirus serotypes) followed by 3 doses of bivalent OPV (bOPV) (which contains Sabin strain types 1 and 3). In 2016, the year after the Global Polio Eradication Initiative (GPEI) Global Certification Commission* certified the eradication of type 2 wild poliovirus (WPV2) ( 2), China joined a global, synchronized effort to cease the use of type 2 oral poliovirus vaccine (OPV2). Integrated AFP, environmental, and immunodeficiency-associated VDPV (iVDPV) surveillance is critical to detecting and containing all polioviruses and achieving the goal of global polio eradication. In 2022, type 3 VDPV (VDPV3) was detected in stool specimens from an infant with primary immunodeficiency disorder (PID) through a pilot surveillance program to identify VDPVs in children with PIDs. Identification of circulating polioviruses relies on surveillance of acute flaccid paralysis (AFP) and environmental surveillance of wastewater (i.e., sewage).
In addition, OPV has resulted in rare cases of vaccine-associated paralytic poliomyelitis (VAPP) among vaccine recipients or their close contacts ( 1). However, among undervaccinated communities and persons with immunodeficiency, OPV mutations that arise during prolonged replication can result in the emergence of genetically divergent, neurovirulent vaccine-derived polioviruses (VDPVs). Sabin-strain OPV contains live attenuated virus and induces immunity by replicating in the intestinal tract, triggering an immune response that clears the vaccine virus. Oral poliovirus vaccine (OPV) has proven to be highly effective in the global effort to eradicate poliomyelitis because of its ability to induce both humoral and intestinal immunity, ease of administration, and low cost ( 1).
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