Experience With Inactivated Polio Vaccine Introduction and the “Switch” From Trivalent to Bivalent Oral Polio Vaccine in the World Health Organization’s Western Pacific Region

Abstract

The World Health Organization (WHO) Western Pacific Region (WPR) has maintained its polio-free status since 2000. The emergence of vaccine-derived polioviruses (VDPVs), however, remains a risk, as oral polio vaccine (OPV) is still used in many of the region’s countries, and pockets of unimmunized or underimmunized children exist in some countries. From 2014 to 2016, the region participated in the globally coordinated efforts to introduce inactivated polio vaccine (IPV) into all countries that did not yet include it in their national immunization schedules, and to “switch” from trivalent OPV (tOPV) to bivalent OPV (bOPV) in all countries still using OPV in 2016.As of September 2016, 15 of 17 countries and areas that did not use IPV by the end of 2014 had introduced IPV. Introduction in the remaining 2 countries has been delayed because of the global shortage of IPV, making it unavailable to select lower-risk countries until the fourth quarter of 2017. All 16 countries using OPV as of 2016 successfully withdrew tOPV during the globally synchronized switch from April to May 2016, and 15 of 16 countries introduced bOPV at the same time, with the remaining country introducing it within 30 days. While countries were primarily responsible for self-funding these activities, additional support was provided.The main challenges encountered in the Western Pacific Region with both IPV introduction and the tOPV-bOPV switch were related to overcoming regulatory policies and challenges with vaccine procurement. As a result, substantial lead time was needed to resolve procurement and regulatory issues before the introductions of IPV and bOPV. As the global community prepares for the full removal of all OPV from immunization programs, this need for lead time and consideration of the impact on national policies should be considered.

The Molecular Evolution of Type 2 Vaccine-Derived Polioviruses in Individuals with Primary Immunodeficiency Diseases

“…Although there is no substantial evidence of polio outbreaks caused by cVDPV2 derived from iVDPV2 excretors, the relative risk of long-term iVDPV2 infection will rise as the population with lower intestinal immunity to type 2 poliovirus among the individuals immunized with bOPV and IPV increase [ 10 , 13 , 68 , 69 ]. The WHO Western Pacific Region (WPR) was certified to be wild polio-free since 2000, except for several importations of wild polioviruses from endemic countries [ 70 , 71 , 72 ]. Since 2001, several cVDPV outbreaks were reported in the WPR; however, all of them were effectively controlled using supplemental OPV immunization [ 60 , 73 , 74 ].…”

Polio and Its Epidemiology

“…Eradication, which is tantalizingly close, will require substantial changes in vaccination policy and practice [160]. We have witnessed the disruptions that were caused in routine vaccination programs and in all facilities in every country including PEFs and non-PEFs within the global polio laboratory network when WPV2 was declared eradicated and phase 2 of GAP III put into operation for containment of material containing or potentially containing PV2 [381,[383][384][385][386][387][388][389][390][391][392][393][394][395][396]. Eradication of WPV3 will be declared in the very near future.…”

Addressing the Challenges and Opportunities of the Polio Endgame: Lessons for the Future

“…While coordination and support from the global level was important, implementation ultimately occurred at the national level with support from regional offices of the WHO and UNICEF and local implementation partners. Colleagues from the regional offices discussed the challenges and creative solutions implemented at the regional and national levels when introducing IPV [65][66][67][68][69].…”