The Long Last Mile of Polio Eradication

Polio eradication programs are in a tough situation once again following a series of reversals in Africa, and the imminent threat of spread in Europe, North America, and other parts of the world. These reversals initially hit the programs when the world was still reeling under the COVID-19 pandemic and the effects of the backslide caused by the syndemic were palpable in the domain of health care, especially immunization. Now, when we are reassessing our priorities in the postpandemic era, polio appears as the only Public Health Emergency of International Concern. Polio’s return to areas that had been polio free for decades changes the entire epidemiological map.[1,2] This reemergence cannot be explained by virology alone. A web of causation including a serious decline in childhood vaccination rates is confounded by wider vaccine hesitancy and cultural resistance to vaccination. In this scenario, anyone not vaccinated against polio is at risk – regardless of location and region. All countries must maintain high vaccination coverage and robust disease surveillance to prevent further setbacks. The year 2024 has started with mixed trends. The world celebrated the tenth anniversary of wild-polio-free certification for Southeast Asia Region, and there is a new resolve among all the actors to surmount the emerging difficulties while preparing for the final ascent. On the other hand, the specter of the continued spread of the wild virus as well as vaccine-derived viruses is offsetting the progress made so far. While Pakistan and Afghanistan are trying to interrupt the transmission of wild poliovirus 1 (WPV1), the two surviving genetic clusters, YB3C and YB3A continue to be endemic. At the time, this editorial is being written, 2 new cases of WPV1 have been confirmed from each of these two countries. WPV1 has also been reported from 95 other sources from Pakistan and 15 other sources from Afghanistan. These other sources include environmental samples, selected contacts, and healthy children. Furthermore, circulating vaccine-derived poliovirus 2 (cVDPV2) has been recently reported from Angola, Liberia, Senegal, Sierra Leone, and South Sudan. These are newly reinfected countries. Ivory Coast has reported a rapid increase in the environmental samples testing positive. A recurrence of cVDPV2 (three new cases), a case of VDPV1 (under investigation), and an environmental sample testing positive has been reported from Indonesia.[1] A new generation polio vaccine - novel oral polio vaccine type 2 (nOPV2) was rolled out in 2021 as a safe and effective tool against cVDPV2. Till now, around 1 billion doses have been administered across 35 countries. This is the first ever vaccine with prequalification approval, granted in December 2023, under Emergency Use Listing of the World Health Organization. This step forward will empower many more countries to use nOPV2 and to evolve a better response against cVDPV2 outbreaks.[3,4] The new vaccine is 80% less likely to seed cVDPV2, but there are concerns around this modality as well. Since 2021, we have seen 14 nOPV2-derived cVDPV2 emergence groups. Of the 8 new emergences in 2023, six originated from nOPV2. A complete switch to injectable polio vaccine is to be implemented with urgency. Continued use of any oral vaccine will soon be incompatible with the goal of eradication. The upside about the reversal events is that in most of these, local surveillance was sensitive enough to detect and inform timely. The downside is that what is detected may just be the tip of the iceberg. Detection of vaccine-derived virus in environmental samples in the USA, Canada, UK, and Israel in the last 2 years underlines this threat.[2] Polio anywhere is a threat to children everywhere. It will always be just a plane ride away until we eradicate it. Once the wild poliovirus transmission is stopped in the remaining two endemic countries, Pakistan and Afghanistan, the endgame-posteradication interface will gain more significance. We will have to assure delivery of at least one dose of affordable inactivated polio vaccine through routine immunization, especially in the high-risk areas. This would finally pave the way for simultaneous global cessation of all oral polio vaccines but not before certain conditions are met. The sensitivity of surveillance will be absolutely critical before the globally synchronized withdrawal of all Sabin polioviruses. This leap forward would intensify the phase of facility containment, already on course for poliovirus types 2 and 3. Finally, with the global certification of wild poliovirus eradication, the world will enter a new era with some added responsibilities for preparedness against probable reemergence on one hand and the transition to programs facing other public health challenges on the other. Maintaining eradication status would demand a continued global commitment for nearly a decade in the postpolio era and this will involve a robust emergency response capacity with transnational cooperation. A sensitive surveillance system and facility containment would again be essential parallel arms during the posteradication vigil. On the research and knowledge generation front, developing newer tools for emergency response, including antivirals, will be a major area of attention. Above all, we cannot lose sight of the dwindling motivation and fatigue among our frontline polio workers who are giving their best in some of the most hostile circumstances. It is unfortunate to note here that their contribution is largely undocumented while we keep celebrating the “celebrated.” Many of our “infantry soldiers” were killed, injured seriously, or abducted at the “line of control.” Most of them were mothers themselves. Many of them are not even listed and they do not have an audible voice in the program ecosystems. We do not easily find a comprehensive record of polio workers killed or seriously injured in action. According to rough estimates, more than 200 polio workers and security personnel have lost their lives in Pakistan and Afghanistan alone, since 2012.[5] Similar violence has been witnessed in several other countries, especially Somalia and Nigeria. In this context, the biggest and most difficult roadblock is the violent religious resistance against modern health-care interventions. Another persistent barrier is the invisible wall of political correctness that often comes in the way of rational thinking. We all understand that public health is a delicate mix of science, policies, programs, and people’s sensitivities. This mix works well till the irrational and violent assertions are not allowed to smother the essence of public health, but when such actors start invading the decision-making processes, the mix starts falling apart. Over the decades, we have gradually allowed aggressive and irrational demands to misrepresent people’s sensitivities. People whom these groups claim to serve are actually held hostage. In several hotspot countries, top-level technical decisions are vetted and censored by religious bodies with devastating impact.[6] Many of such religious bodies are state supported or even state appointed. Emboldened by such retreat, sometimes capitulation, by the organs of governance, the religious groups are more likely to attack the frontline workers even in apparently peaceful areas. Frontline workers in such difficult settings may develop a depressing perception that the public health elite is no different from top bureaucrats and political actors. Negotiating with the hounds to keep the hare running is a cynical idea in itself. We fully understand that disease eradication is not merely a technical mission. Science, art and diplomacy of public health have brought us this far. But from now on, the long and very steep last mile needs to be crossed. For this final ascent, we must hold the hands of our frontline colleagues to assure that the world is with them and not with their attackers.

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