The Last Mile in Polio Eradication: Program Challenges and Perseverance

Abstract

As the Global Polio Eradication Initiative (GPEI) strategizes towards the final steps of eradication, routine immunization schedules evolve, and high-quality vaccination campaigns and surveillance systems remain essential. New tools are consistently being developed, such as the novel oral poliovirus vaccine to combat outbreaks more sustainably, as well as non-infectiously manufactured vaccines such as virus-like particle vaccines to eliminate the risk of resurgence of polio on the eve of a polio-free world. As the GPEI inches towards eradication, re-strategizing in the face of evolving challenges and preparing for unknown risks in the post-certification era are critical.

Keywords: Global Polio Eradication Initiative; immunization; outbreak response; poliomyelitis; vaccine-derived poliovirus.

Figure 4

Emergences of cVDPV2 in 2016–2023 after the tOPV-to-bOPV switch linked to OPV use. The figure depicts the use of Sabin OPV (mOPV2 and tOPV) for outbreak response and the introduction of nOPV2 in March 2021. The data are from 1 July 2016, to 31 December 2023. Figure from Bandyopadhyay et al., 2024 [40]. Abbreviations: cVDPV2, type 2 circulating vaccine-derived poliovirus; tOPV, trivalent oral poliovirus vaccine; bOPV, bivalent oral poliovirus vaccine; mOPV2, type 2 monovalent oral poliovirus vaccine; nOPV2, novel type 2 oral poliovirus vaccine.

Figure 1

2023 global overview of positive poliovirus isolates, including types 1, 2, and 3 wild poliovirus (WPV) and circulating vaccine-derived poliovirus (cVDPV). Clinical acute flaccid paralysis (AFP) and environmental surveillance (ES) poliovirus detections are depicted. On the left, there is a per-country list of the latest detections of AFP and ES. Data source: from WHO HQ as of 27 February 2024.; figure adapted from internal WHO HQ figures; map creation 5 April 2024; map produced by WHO GIS Centre for Health, DNA/DDI. Disclaimer: The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the WHO concerning the legal status of any country, territory, city, or area or of its authorities or concerning the delimitation of its frontiers or boundaries. Dotted and dashed lines on maps represent approximate border lines for which there may not yet be full agreement.

Figure 2

Case count of global clinical AFP poliovirus cases in the past decade (2013–2023) including WPV1 and cVDPV types 1, 2, and 3. Data from WHO HQ as of 27 February 2024. Abbreviations: cVDPV, circulating vaccine-derived poliovirus; WPV, wild-type poliovirus; AFP, acute flaccid paralysis.

Figure 3

Routine polio immunization schedules of countries using inactivated poliovirus vaccines (IPVs) or IPVs plus oral poliovirus vaccines (OPVs) administered sequentially. Data source: WHO as of December 2023; map creation date 05 April 2024; map production by WHO GIS Centre for Health, DNA/DDI. Disclaimer: The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of WHO concerning the legal status of any country, territory, city, or area or of its authorities or concerning the delimitation of its frontiers or boundaries. Dotted and dashed lines on maps represent approximate border lines for which there may not yet be full agreement.