The Global Polio Eradication Initiative (GPEI) has missed every target it has set for more than a decade. The 2019 deadline came and went. So did 2023. So did 2025. Along the way the campaign has racked up one of the most staggering success stories in public health history and, simultaneously, found itself trapped in geopolitical and social conditions the eradication playbook was never designed to handle.
The numbers tell both stories at once. Wild poliovirus has been driven down 99.98 percent from 350,000 cases per year across 125 countries in the 1980s to just 52 cases globally in 2025. A modeling study by Badizadegan and colleagues in 2022 estimated that the campaign has prevented between 2.5 million and 6 million cases of paralysis. So far in 2026, the world has recorded 14 cases. By any conventional measure, the effort has nearly worked.
But nearly worked is not eradicated. The virus that remains is concentrated in a belt straddling Afghanistan and Pakistan, where conditions required for the classic eradication model (territorial control by a functioning state, trust in public health institutions, and safe access for health workers) have broken down. The GPEI has spent more than US$3 billion in those two countries over the past decade. An estimated 100,000 children still live in districts vaccinators cannot reach. Some districts report immunization coverage below 50 percent.
The core structural tension is this: the eradication strategy was designed during an era when governments largely controlled their territory and populations broadly trusted vaccines. The last reservoirs of polio now lie in places where neither condition holds. The machine that got the world 99.98 percent of the way cannot complete the final 0.02 percent because the political and social landscape has shifted beneath it.
The Twin-Vaccine Dilemma
The scientific toolkit is deceptively simple and brutally unforgiving. Two vaccines exist. The oral polio vaccine (OPV) uses live attenuated virus, generates powerful gut immunity that blocks transmission, and is cheap to administer: a few drops on the tongue. It is the workhorse that drove polio from 125 countries to two. But OPV carries a documented risk: in underimmunized populations, the weakened virus in the vaccine can circulate and mutate back into a paralytic form, causing vaccine-derived polio outbreaks.
The inactivated polio vaccine (IPV), by contrast, uses killed virus. It protects the individual against paralysis but does not stop the virus from being shed and transmitted to others. IPV is an insurance policy for the individual, not a tool for interrupting transmission chains.
The eradication logic therefore runs through three stages. First, use OPV to stamp out wild poliovirus everywhere. Second, withdraw OPV carefully and sequentially to prevent the vaccine-derived cases that emerge when coverage gaps allow the attenuated virus to recover its virulence. Third, transition to IPV as a long-term protection measure once transmission is truly gone. The strategy works perfectly when every child can be reached and coverage is high. It breaks down when large pockets of children are persistently missed, because missed children become the breeding ground for new outbreaks. The tool used to protect them paradoxically becomes the source of the threat.
Vaccine-derived polio cases peaked at 882 in 2022, concentrated in sub-Saharan Africa, and have been declining year on year since. But the trend will only stay downward if the campaign can keep reaching children who would otherwise fall through the gaps.
The Unreachable Districts
In 2025, the GPEI’s Independent Monitoring Board issued a warning that captured the depth of the impasse. For the first time in the history of polio eradication, the board noted, it did not feel as if Afghanistan was, or wanted to be, involved in the effort.
The situation on the ground bears that out. Violence between Pakistan and Afghanistan has destabilized border areas that represent the last active transmission corridors. In southern Afghanistan, a ban on female vaccinators has crippled house-to-house campaigns, because in much of the region only women can gain entry to homes and reach children. In 2026, at least four police guards assigned to protect vaccination teams were killed. In parts of south Pakistan, entire districts have been unreachable for extended periods.
Arshad Quddus, the acting director of the GPEI, has described the situation in Khyber Pakhtunkhwa as a complex, messy environment without a clearly identifiable group to negotiate with. This matters because the standard tool for reaching children in conflict zones has been humanitarian pause negotiations, the same approach that, as David Salisbury, chair of the GPEI certification body, has noted, succeeded in eradicating polio from northeast Nigeria despite Boko Haram and from Gaza. But those successes relied on organized, hierarchical armed groups capable of enforcing a commitment. In the last reservoirs, the violence is diffuse, the actors fragmented, and the negotiating counterparties unclear.
Cross-border movement between Pakistan and Afghanistan further complicates the picture. People, and viruses, do not respect administrative boundaries. Even if one country makes progress, the other can replenish the viral reservoir in a matter of weeks.
The Funding Squeeze
The geopolitical headwinds are not limited to the conflict zones. The broader international architecture that sustained the campaign for decades is showing cracks.
The United States withdrawal from the World Health Organization and the dismantling of USAID have disrupted infrastructure the polio campaign relied upon. The United Kingdom has ceased contributions. The funding crisis forced a 30 percent budget cut for the GPEI in 2026. The Gates Foundation pledged US$1.2 billion in December 2025, reducing the shortfall but not eliminating it.
The consequences of the cuts are visible in the campaign’s operational decisions. Faced with a reduced budget, the GPEI has scaled back OPV immunization in areas not currently experiencing outbreaks. Models consistently show that preemptive vaccination in these areas is essential to stamp out future outbreaks. The cuts trade a certain cost in the present for a larger risk in the future.
The Independent Monitoring Board warned in 2025 that political will was waning. That is a profound statement for an initiative that has, for more than three decades, depended on the sustained commitment of donor governments and recipient countries alike.
The Search for a Plan B
As the campaign finds itself caught between scientific possibility and operational impossibility, a quiet reckoning is underway among the researchers and policymakers who have spent their careers on this problem.
Kimberly Thompson of Kid Risk has argued that while eradication remains theoretically possible, it is practically unattainable on the current trajectory, in effect arguing that it has already failed by the standards the initiative set for itself. This is not an argument about the science. The tools work. The transmission dynamics are understood. As Isobel Blake of Imperial College has put it, the challenges are operational, not scientific.
That distinction cuts to the heart of the matter. The eradication model was built for a world in which the operational problems were logistical: getting cold-chain equipment into remote villages, training vaccinators, tracking coverage. Those problems have largely been solved. The new operational problems involve armed groups that cannot be negotiated with, populations that have lost trust in health systems, and governments unable or unwilling to control their territory.
What a Plan B might look like is not yet clear. Some researchers have begun modeling scenarios in which eradication is replaced by a long-term containment strategy: holding polio at very low levels indefinitely through sustained vaccination, accepting that the virus will not be eliminated but that its burden can be kept minimal. Others argue that this would be a catastrophic retreat, that perpetual vaccination and surveillance would eventually cost more than finishing the job, and that the scientific window for eradication will not stay open forever.
The GPEI’s experience in northeast Nigeria and Gaza suggests that the model can still work when the conditions are right: when there is a counterparty to negotiate with, a humanitarian corridor to open, a community that wants its children protected. The question is whether the conditions in the last reservoirs can be made right, or whether the world needs a fundamentally different strategy for a world that no longer looks like the one the strategy was designed for.
Fourteen cases in 2026. An estimated 100,000 children beyond reach. A budget cut of 30 percent. The polio campaign has done the hard work of getting to the last mile. It is now discovering that the last mile runs through terrain the map was not drawn for.