Polio eradication: what kind of world do we want?
Authors: Kimberly M Thompson
Journal: The Lancet Infectious Diseases (2021)

Achieving the 1988 World Health Assembly commitment of global eradication of poliomyelitis1World Health AssemblyGlobal eradication of poliomyelitis by the year 2000 (resolution 41.28).http://www.who.int/csr/ihr/polioresolution4128en.pdfDate: 1988Date accessed: July 22, 2021Google Scholar will require ending the transmission of all three types (1, 2, and 3) of wild polioviruses and use of oral poliovirus vaccine (OPV).2Dowdle WR de Gourville E Kew OM Pallansch MA Wood DJ Polio eradication: the OPV paradox.Rev Med Virol. 2003; 13: 277-291Crossref PubMed Scopus (116) Google Scholar Although extremely rare, OPV can cause vaccine-associated paralytic polio in immunologically naive recipients or close contacts upon first exposure.3Duintjer Tebbens RJ Pallansch MA Kew OM et al.Risks of paralytic disease due to wild or vaccine-derived poliovirus after eradication.Risk Anal. 2006; 26: 1471-1505Crossref PubMed Scopus (148) Google Scholar In addition, when used in populations with low immunisation coverage, OPV can continue to circulate, instead of dying out, and lose its attenuating mutations as it spreads.3Duintjer Tebbens RJ Pallansch MA Kew OM et al.Risks of paralytic disease due to wild or vaccine-derived poliovirus after eradication.Risk Anal. 2006; 26: 1471-1505Crossref PubMed Scopus (148) Google Scholar Continued transmission of OPV-related viruses can lead to polio outbreaks caused by circulating vaccine-derived polioviruses (cVDPVs) that behave like wild-type polioviruses.3Duintjer Tebbens RJ Pallansch MA Kew OM et al.Risks of paralytic disease due to wild or vaccine-derived poliovirus after eradication.Risk Anal. 2006; 26: 1471-1505Crossref PubMed Scopus (148) Google Scholar Countries and the Global Polio Eradication Initiative (GPEI) have made substantial progress toward polio eradication,4Thompson KM Kalkowska DA An updated economic analysis of the Global Polio Eradication Initiative.Risk Anal. 2021; 41: 393-406Crossref PubMed Scopus (18) Google Scholar although as of early 2020 (before the COVID-19 pandemic was declared), GPEI was not on-track to succeed by the target year of 2023.5Thompson KM Poliovirus vaccine options: another step forward.Lancet. 2020; 397: 2-3Summary Full Text Full Text PDF PubMed Scopus (3) Google Scholar One major victory came with the last reported case caused by type 2 wild poliovirus in 1999, and certification of global eradication of indigenous type 2 wild poliovirus transmission in 2015.6WHO14th meeting of the Global Commission for Certification of Poliomyelitis Eradication (GCC), Bali, Indonesia. Sept 20–21, 2015. Summary of findings, decisions and recommendations.http://polioeradication.org/wp-content/uploads/2016/07/1Report.pdfDate: 2015Date accessed: July 22, 2021Google Scholar After an extensive, multiyear planning process, GPEI globally coordinated the cessation of all routine use of type 2-containing OPV (OPV2) in April–May, 2016.7Hampton LM Farrell M Ramirez-Gonzalez A et al.Cessation of trivalent oral poliovirus vaccine and introduction of inactivated poliovirus vaccine—worldwide, 2016.MMWR. 2016; 65: 934-938Crossref PubMed Scopus (153) Google Scholar OPV cessation represented an essential step toward the promise of a world free of type 2 polio, but unfortunately OPV2 cessation did not end type 2 polio. Before OPV2 cessation, some countries failed to stop transmission of existing type 2 cVDPVs (cVDPV2s) or to achieve sufficiently high population immunity to prevent their emergence after OPV2 cessation, which necessitated outbreak responses using monovalent OPV2 (mOPV2) after mid-2016.8Macklin GR O'Reilly KM Grassly NC et al.Evolving epidemiology of poliovirus serotype 2 following withdrawal of the serotype 2 oral poliovirus vaccine.Science. 2020; 368: 401-405Crossref PubMed Scopus (87) Google Scholar After OPV2 cessation, other countries reintroduced mOPV2 in response to outbreaks or environmental evidence of type 2 transmission.8Macklin GR O'Reilly KM Grassly NC et al.Evolving epidemiology of poliovirus serotype 2 following withdrawal of the serotype 2 oral poliovirus vaccine.Science. 2020; 368: 401-405Crossref PubMed Scopus (87) Google Scholar In 2020, more than half of the 1073 global reported cVDPV2 cases occurred in 20 African countries (figure A), which far exceeded the 140 reported global cases of type 1 wild poliovirus in 2020. In early 2020, the increasing annual number of cVDPV2 cases reported since 2018 (figure A) and atypical outbreaks in 20198Macklin GR O'Reilly KM Grassly NC et al.Evolving epidemiology of poliovirus serotype 2 following withdrawal of the serotype 2 oral poliovirus vaccine.Science. 2020; 368: 401-405Crossref PubMed Scopus (87) Google Scholar led GPEI to restart OPV2 production.5Thompson KM Poliovirus vaccine options: another step forward.Lancet. 2020; 397: 2-3Summary Full Text Full Text PDF PubMed Scopus (3) Google Scholar Since 2016, 24 countries in Africa have reported cVDPV2 cases (figure B). In The Lancet Infectious Diseases, Laura V Cooper and colleagues statistically model epidemiological data from 51 African countries to characterise median changes (with IQRs) in type 2 polio immunity in children under 5 years old for 6-month periods between January–June, 2016, and January–June, 2020.9Cooper LV Bandyopadhyay AS Gumede N et al.Risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance data for 51 countries in Africaa.Lancet Infect Dis. 2021; (published online Oct 11.)https://doi.org/10.1016/S1473-3099(21)00453-9PubMed Google Scholar Consistent with the timing of OPV2 cessation and the introduction of inactivated poliovirus vaccine (IPV), the analysis shows a substantial decline in OPV2-induced immunity in children under 5 years from 87% (IQR 81–93) in January–June, 2016, to 14% (9–37) in January–June, 2020, while IPV-induced immunity for type 2 for the same time period increased from 3% (IQR <1–6%) to 35% (IQR 24–47).9Cooper LV Bandyopadhyay AS Gumede N et al.Risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance data for 51 countries in Africaa.Lancet Infect Dis. 2021; (published online Oct 11.)https://doi.org/10.1016/S1473-3099(21)00453-9PubMed Google Scholar Decreased levels of OPV-induced and IPV-induced immunity represented notable risk factors for cVDPV2 cases in the next 6-month period.9Cooper LV Bandyopadhyay AS Gumede N et al.Risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance data for 51 countries in Africaa.Lancet Infect Dis. 2021; (published online Oct 11.)https://doi.org/10.1016/S1473-3099(21)00453-9PubMed Google Scholar Considering the role of mOPV2 outbreak responses, Cooper and colleagues report lower risks of cVDPV2 cases associated with mOPV2 use in the previous 6 months, and showed that outbreak response vaccination campaigns in Africa did not stop the spread of cVDPV2s.9Cooper LV Bandyopadhyay AS Gumede N et al.Risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance data for 51 countries in Africaa.Lancet Infect Dis. 2021; (published online Oct 11.)https://doi.org/10.1016/S1473-3099(21)00453-9PubMed Google Scholar Overall, they estimate that, within 6 months, the actual outbreak response campaigns in Africa covered only 11% of the predicted at-risk population of children under 5 years.9Cooper LV Bandyopadhyay AS Gumede N et al.Risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance data for 51 countries in Africaa.Lancet Infect Dis. 2021; (published online Oct 11.)https://doi.org/10.1016/S1473-3099(21)00453-9PubMed Google Scholar Sadly, these sobering results should come as no surprise. Extensive prospective modelling done to support OPV2 cessation risk management identified threats and essential risk management strategies.10Thompson KM Kalkowska DA Review of poliovirus modelling performed from 2000-2019 to support global polio eradication.Expert Rev Vaccines. 2020; 19: 661-686Crossref PubMed Scopus (37) Google Scholar Notably, studies highlighted the need to increase population immunity in some countries using trivalent OPV before stopping OPV2,10Thompson KM Kalkowska DA Review of poliovirus modelling performed from 2000-2019 to support global polio eradication.Expert Rev Vaccines. 2020; 19: 661-686Crossref PubMed Scopus (37) Google Scholar, 11Thompson KM Duintjer Tebbens RJ Modelling the dynamics of oral poliovirus vaccine cessation.J Infect Dis. 2014; 210: S475-S484Crossref PubMed Scopus (72) Google Scholar and anticipated that IPV introduction could slightly reduce poliomyelitis cases in the event of outbreaks, although IPV use would not prevent or stop transmission, and could delay the detection, of cVDPV2s.10Thompson KM Kalkowska DA Review of poliovirus modelling performed from 2000-2019 to support global polio eradication.Expert Rev Vaccines. 2020; 19: 661-686Crossref PubMed Scopus (37) Google Scholar, 12Duintjer Tebbens RJ Thompson KM Modelling the potential role of inactivated poliovirus vaccine to manage the risks of oral poliovirus vaccine cessation.J Infect Dis. 2014; 210: S485-S497Crossref PubMed Scopus (43) Google Scholar Other studies emphasised the need to respond aggressively to evidence of transmission of OPV2-related viruses with rapid, high-coverage, and sufficiently large mOPV2 campaigns to quickly shut down outbreaks;10Thompson KM Kalkowska DA Review of poliovirus modelling performed from 2000-2019 to support global polio eradication.Expert Rev Vaccines. 2020; 19: 661-686Crossref PubMed Scopus (37) Google Scholar, 13Duintjer Tebbens RJ Pallansch MA Wassilak SGF Cochi SL Thompson KM Characterization of outbreak response strategies and potential vaccine stockpile needs for the polio endgame.BMC Infecti Dis. 2016; 16: 137Crossref PubMed Scopus (46) Google Scholar and demonstrated the expected increasing vulnerability of populations to restarting transmission of type 2 polioviruses with increasing time since OPV2 cessation.10Thompson KM Kalkowska DA Review of poliovirus modelling performed from 2000-2019 to support global polio eradication.Expert Rev Vaccines. 2020; 19: 661-686Crossref PubMed Scopus (37) Google Scholar, 14Duintjer Tebbens RJ Hampton LM Thompson KM Implementation of coordinated global serotype 2 oral poliovirus vaccine cessation: risks of inadvertent trivalent oral poliovirus vaccine use.BMC Infect Dis. 2016; 16: 237Crossref PubMed Scopus (36) Google Scholar The analysis of epidemiological evidence by Cooper and colleagues9Cooper LV Bandyopadhyay AS Gumede N et al.Risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance data for 51 countries in Africaa.Lancet Infect Dis. 2021; (published online Oct 11.)https://doi.org/10.1016/S1473-3099(21)00453-9PubMed Google Scholar provides a retrospective confirmation of the predictions of the prospective models that anticipated the consequences of failures if poliovirus policy makers did not manage risks well. What went wrong, and why was the GPEI not on track to meet targets even before the disruptions caused by the COVID-19 pandemic? While some might blame predictive models for suggesting that optimal outcomes were achievable, actual public health outcomes depend on the actions and decisions of policy makers and their implementation.15Thompson KM Kalkowska DA Reflections on modelling poliovirus transmission and the polio eradication endgame.Risk Anal. 2021; 41: 229-247Crossref PubMed Scopus (26) Google Scholar For example, prospective modelling suggested that aggressive mOPV2 use in well performed, rapid, and sufficiently large immunisation campaigns shortly after stopping OPV2 could shut down transmission,13Duintjer Tebbens RJ Pallansch MA Wassilak SGF Cochi SL Thompson KM Characterization of outbreak response strategies and potential vaccine stockpile needs for the polio endgame.BMC Infecti Dis. 2016; 16: 137Crossref PubMed Scopus (46) Google Scholar and this strategy worked where implemented (eg, Syria).8Macklin GR O'Reilly KM Grassly NC et al.Evolving epidemiology of poliovirus serotype 2 following withdrawal of the serotype 2 oral poliovirus vaccine.Science. 2020; 368: 401-405Crossref PubMed Scopus (87) Google Scholar However, as Cooper and colleagues showed,9Cooper LV Bandyopadhyay AS Gumede N et al.Risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance data for 51 countries in Africaa.Lancet Infect Dis. 2021; (published online Oct 11.)https://doi.org/10.1016/S1473-3099(21)00453-9PubMed Google Scholar poor implementation of cVDPV2 outbreak responses led to disappointing consequences in Africa. In addition, the unexplained emergences of OPV2-related viruses in Africa and Pakistan in 2019 raise even more difficult questions about OPV cessation and global poliovirus containment, and point to the absence of accountability in a global programme that requires a winning strategy, aligned partners, effective tactics, necessary and sufficient resources, and meticulous management of globally interdependent risks to succeed. As the post-COVID-19 polio endgame unfolds, global leaders need to decide how the world will manage the globally interdependent risks posed by some infectious diseases, including polio, COVID-19, and future pandemic threats, at a time of increased focus by some on non-communicable diseases, decentralisation, regionalisation, and nationalisation. The current situation with polio eradication and the global experience with COVID-19 show that the current management approach for globally interdependent risks, at least those posed by some infectious diseases, is not working. The analysis by Cooper and colleagues9Cooper LV Bandyopadhyay AS Gumede N et al.Risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance data for 51 countries in Africaa.Lancet Infect Dis. 2021; (published online Oct 11.)https://doi.org/10.1016/S1473-3099(21)00453-9PubMed Google Scholar should serve as a reminder that polio is still not gone, including from Africa, despite its recent victory of regional certification as free of transmission of all three types of indigenous wild polioviruses—and that the world continues to miss an opportunity to rid current and future generations of a once terrifying disease. Despite many setbacks, eradication of polio is possible in our highly imperfect and inequitable world if global leaders can negotiate the path as they once did with smallpox. Now is the time to ask: what kind of world do we want, and how do we get there from here? This online publication has been corrected. The corrected version first appeared at thelancet.com/infection on October 18, 2021 This online publication has been corrected. The corrected version first appeared at thelancet.com/infection on October 18, 2021 I declare no competing interests. Risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance data for 51 countries in AfricaOur findings suggest that as mucosal immunity declines, larger or faster responses with vaccination campaigns using type 2-containing OPV will be required to stop cVDPV2 transmission. IPV-induced immunity also has an important role in reducing the burden of cVDPV2 poliomyelitis in Africa. Full-Text PDF Open AccessCorrection to Lancet Infect Dis 2021; published online Oct 11. https://doi.org/10.1016/S1473-3099(21)00458-8Thompson KM. Polio eradication: what kind of world do we want? Lancet Infect Dis 2021; published online Oct 11. https://doi.org/10.1016/S1473-3099(21)00458-8—In this Comment, the final sentence of the third paragraph has been reworded to "Overall they estimate that, within 6 months, the actual outbreak response campaigns in Africa covered only 11% of the predicted at-risk population of children under 5 years". This correction has been made to the online version as of oct 18, 2021, and will be made to the printed Comment. Full-Text PDF