Final Frontiers of the Polio Eradication Endgame

Ananda S. Bandyopadhyay; Grace R. Macklin

Disclosures

Curr Opin Infect Dis. 2020;33(5):404-410. 

In This Article

Abstract and Introduction

Abstract

Purpose of Review: Focusing on the key developments since January 2019, this review aims to inform policymakers and clinical practitioners on the latest on evolving global polio epidemiology and scientific advancements to guide strategies for eradication.

Recent Findings: An upsurge in wild poliovirus type 1 cases in Pakistan and Afghanistan and an expansion of type 2 circulating vaccine-derived poliovirus transmission in multiple countries threaten the remarkable progress made over past several decades by the global eradication program. These challenges have also spurred innovation on multiple fronts, including earlier detection, enhanced environmental surveillance and safer and more affordable vaccine options.

Summary: A concerted effort to adapt program strategies to address context-specific challenges and continued focus on innovations to enhance detection and response capabilities will be the key to achieve and sustain eradication of all types of polioviruses.

Introduction

Four decades since its certification of eradication, smallpox remains the only human disease to be eradicated. Two decades from its original target date, polio eradication continues to remain enticingly close to the finish line. The overall disease incidence of polio has been reduced by 99.9% from the time the global polio eradication initiative (GPEI) was launched in 1988. Two of the three wild types of polio have been certified eradicated, with only wild polio virus type 1 (WPV1) circulating in two countries – Pakistan and Afghanistan.[1] However, WPV1 transmission in these two countries intensified in recent years, with number of paralyzed children from WPV1 five times higher in 2019 compared with 2018, a concerning setback from the consistent decline in disease incidence over the past decade (Figure 1). In addition, circulating vaccine-derived poliovirus (cVDPV) transmission is rapidly spreading with outbreaks reported from nearly 20 countries from four different WHO Regions (African, Eastern Mediterranean, South-east Asian, and Western Pacific) (Figure 2).[2,3] Moreover, the coronavirus disease-2019 (COVID-19) pandemic has resulted in temporary suspension of supplementary immunization activities (SIAs) in polio-infected countries since early 2020 leading to a heightened risk of further spread of poliovirus in the coming months.[4]

Figure 1.

(a) Use of different oral poliovirus vaccines in outbreak response over time. (b) Incidence of poliomyelitis cases from wild poliovirus and circulating vaccine-derived poliovirus, January 2000 – June 2020. *Cases for 2020 are those in the period 01 January to 01 June only. Data as of 03 June 2020. bOPV, bivalent oral polio vaccines; mOPV, monovalent OPV; nOPV, novel OPV; tOPV, trivalent OPV.

Figure 2.

Countries with reported poliomyelitis cases from wild poliovirus and circulating vaccine-derived poliovirus, 01 January 2019 – 01 June 2020. Data as of 03 June 2020.

On the basis of the evolving global epidemiologic situation, the current focus for achieving and sustaining eradication is centered on a few strategic priorities, which include: improving quality of outbreak response; accelerating development of vaccines that have less risk of reversion to neurovirulence; enhancing surveillance scope and efficiency; and strengthening routine immunization activities.[5] In this review, we summarize the most recent advances on these fronts for a clear understanding of the current challenges and potential solutions to direct the final phase of polio eradication.

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