ABSTRACT
The global polio eradication initiative (gpei) has made steady progress toward the eradication target since its inception in 1988 [1]. the number of paralytic cases due to wild poliovirus has declined worldwide by >99.9%, and 2 of the 3 wild poliovirus serotypes have been declared eradicated by an independent global certification commission: serotype 2 in 2015 and serotype 3 in 2019 [2, 3]. the gpei has implemented the endgame strategic plan 20132018 to accelerate the eradication of wild poliovirus type 1 from its last endemic zones in pakistan and afghanistan. [4]. in addition, the plan called for the sequential removal of the sabin strains from the oral poliovirus vaccine (opv) and the concomitant addition of ≥1 dose of inactivated poliovirus vaccine (ipv) in routine national immunization programs. the removal was needed because the continuing use of live viral vaccines is incompatible with eradication, since these viruses can mutate and recombine, thus reacquiring the neurovirulence and transmission characteristics of wild poliovirus [5]. the burden of paralytic disease caused by vaccine-related polioviruses would not be accepted as the world approaches eradication of wild poliovirus. for example, sabin type 2 was responsible for approximately 40% of the vaccine-associated paralytic poliomyelitis burden and caused 91% of circulating vaccine-derived poliovirus (cvdpv) cases between 2000 and 2016...
