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Background: Elimination of poliovirus in Pakistan and Afghanistan is challenged by notions against the role of oral poliovirus vaccine (OPV) in eradicating contemporary wild poliovirus (WPV) strains.Methods: A total of 1055 WPV type 1 (WPV1) strains isolated between 2013 and 2018 were categorized into 68 antigenic groups and tested for neutralization by OPV-derived antibodies. Molecular docking was conducted to determine neutralization efficiency of antibodies against WPV. The clinical significance of WPV1 variants was assessed to ascertain their role in patient outcomes.Results: We found that 88% of WPV1 strains isolated from paralytic children belonged to a single antigenic lineage identical to the WPV1 strain detected in 1993. WPV1 antigenic variants were effectively neutralized by OPV-derived antibodies, with geometric mean titers comparable to the neutralization titers found for 3 strains in OPV (OPV1-3, 7.96-9.149 [95% confidence interval, 6.864-10.171]; WPV1 strains, 7.542-8.786 [6.493-9.869]). Docking examination underscored a strong antigen-antibody interaction despite variations within the viral protein 1 epitopes. There was no significant association (P = .78) with clinical prognosis among patients infected with antigenically diverse WPV1 strains and patient outcomes, including death.Conclusions: Our findings substantiate the robustness of OPV for neutralizing the contemporary WPV1 strains endemic in Pakistan and Afghanistan. Vaccination coverage must be augmented to achieve early eradication. [ABSTRACT FROM AUTHOR]

Background Pakistan is among 3 countries endemic for wild poliovirus type 1 (WPV1) circulation that are still struggling for eradication of poliomyelitis. Active clinical and environmental surveillance with meticulous laboratory investigations provide insights into poliovirus transmission patterns and genomic diversity to inform decisions for strategic operations required to achieve eradication. Methods We analyzed epidemiological and virological data to comprehend the current epidemiological status of WPV1 in Pakistan during 2015–2017. Stool specimens of patients with acute flaccid paralysis (AFP) and sewage samples collected from 60 environmental sites were tested. Viral culturing, intratypic differentiation by real-time polymerase chain reaction, and nucleic acid sequencing of the VP1 region of the poliovirus genome to determine genetic relatedness among WPV1 strains were applied. Results Poliovirus isolates were grouped into 11 distinct clusters, which had ≥95% nucleotide homology in the VP1 coding region. Most of the poliovirus burden was shared by 3 major reservoirs: Karachi, Peshawar, and Quetta block (64.2% in 2015, 75.4% in 2016, and 76.7% in 2017). Conclusions Environmental surveillance reveals importations and pockets of unimmunized children that dictate intensive target mop-up campaigns to contain poliovirus transmission. A decrease in the number of orphan isolates reflects effective combination of AFP and environmental surveillance in Pakistan. The genetic data reflect sustained transmission within reservoir areas, further expanded by periodic importations to areas of high immunity reflected by immediate termination of imported viruses. Improved immunization coverage with high-quality surveillance is vital for global certification of polio eradication. [ABSTRACT FROM AUTHOR]