Updated Characterization of Poliovirus Transmission in Pakistan and Afghanistan and the Impacts of Different Outbreak Response Vaccine Options

J Infect Dis. 2021 Nov 16;224(9):1529-1538. doi: 10.1093/infdis/jiab160.


Background: Pakistan and Afghanistan remain the only reservoirs of wild poliovirus transmission. Prior modeling suggested that before the coronavirus disease 2019 (COVID-19) pandemic, plans to stop the transmission of serotype 1 wild poliovirus (WPV1) and persistent serotype 2 circulating vaccine-derived poliovirus (cVDPV2) did not appear on track to succeed.

Methods: We updated an existing poliovirus transmission and Sabin-strain oral poliovirus vaccine (OPV) evolution model for Pakistan and Afghanistan to characterize the impacts of immunization disruptions and restrictions on human interactions (ie, population mixing) due to the COVID-19 pandemic. We also consider different options for responding to outbreaks and for preventive supplementary immunization activities (SIAs).

Results: The modeling suggests that with some resumption of activities in the fall of 2020 to respond to cVDPV2 outbreaks and full resumption on 1 January 2021 of all polio immunization activities to pre-COVID-19 levels, Pakistan and Afghanistan would remain off-track for stopping all transmission through 2023 without improvements in quality.

Conclusions: Using trivalent OPV (tOPV) for SIAs instead of serotype 2 monovalent OPV offers substantial benefits for ending the transmission of both WPV1 and cVDPV2, because tOPV increases population immunity for both serotypes 1 and 2 while requiring fewer SIA rounds, when effectively delivered in transmission areas.

Keywords: dynamic modeling; eradication; outbreak response; polio.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Afghanistan / epidemiology
  • COVID-19*
  • Disease Eradication
  • Disease Outbreaks / prevention & control*
  • Humans
  • Pakistan / epidemiology
  • Pandemics
  • Poliomyelitis / epidemiology
  • Poliomyelitis / prevention & control
  • Poliomyelitis / transmission*
  • Poliovirus Vaccine, Oral*
  • Poliovirus* / immunology
  • SARS-CoV-2


  • Poliovirus Vaccine, Oral