The world is ‘stingingly close’ to eradicating polio – and so far this year there have been no confirmed cases of wild polio. But experts warn that vaccination efforts – and funding – must not falter if the world wants to rid itself of a human infectious disease for the future. second time in historyafter smallpox.
No cases of wild polio infection in humans have been reported in the past 19 weeks. Figures from the World Health Organization reveal that the last confirmed cases occurred on the borders of Pakistan and Afghanistan in October and September 2023 respectively; these are the last countries on earth where polio is endemic.
“To have lasted 19 consecutive weeks … is a long period without a single case, therefore there is some hope (of eradication),” said Gordon McInally, president of Rotary International, a founding partner in the Global initiative for polio eradication (GPEI), told the Observer. “All of us involved in this, every week we get an email with the updated numbers… and every week when I click on that email my heart rate goes up until I see the number hoping it will be zero and not one, or worse. But we look at it week by week.”
But those involved in the eradication effort are taking nothing for granted. The program has previously come under fire for its ‘almost-there story’, as described in a report last September by the Independent Monitoring Board, led by Liam Donaldson, a former Chief Medical Officer for England.
Still, McInally said, if they can get through another 33 weeks (a full year after the last case), they will “carefully celebrate,” and if the world remains disease-free for two years, they can officially declare global polio eradication. .
While the absence of confirmed cases is “really encouraging,” Aidan O’Leary, director of polio eradication at the WHO, said: “It’s important that we don’t call the numbers fantastic.” The campaign must be aggressive in closing any gaps in vaccination legislation, he added.
The latest WHO figures show that 34 samples of wild poliovirus were detected from environmental and other sources, including from surveillance samples of sewage (where the virus can circulate) in the first three months of this year. “We are identifying environmental isolates that indicate there is some transmission,” O’Leary said, adding that this should also be zero.
O’Leary, McInally and other stakeholders met with Andrew Mitchell, the Development Minister, and his team on Wednesday to update them on polio, and to ask the British government to continue with the funding, which expires this year. They are asking the Foreign, Commonwealth and Development Office for £100 million over the next two years. GPEI’s goal is to eradicate polio by 2026.
The British government is the second largest contributor to polio eradication after the US, McInally said. He said funding is crucial because “we are at that challenging point in time where because of the geography and the nomadic nature of many of the people we are trying to reach, it is not easy to reach everyone to get it done , and there is the realization that unless we finish it completely, we run the risk of it bubbling up again.”
If they fail to eradicate polio in Afghanistan and Pakistan, WHO modeling suggests there could be a “global resurgence” resulting in around 200,000 new cases of polio per year within a decade. Until this happens, McInally said, polio is just a “plane ride away.” Imported polioviruses caused alarm in 2022 when an unvaccinated adult in New York was paralyzed by the disease, and the poliovirus was found in sewage in London.
But McInally is hopeful, in part because of the program’s success in India. March 27 will mark ten years since the country officially became polio-free. There are some parallels with rural India that give him hope. “A lot of people said, ‘You’ll never get rid of polio from India’… and it happened.”
Vaccinations have been stepped up in Afghanistan and Pakistan; with the program extending the target age for immunizing children from under five to under 10, O’Leary said, and synchronizing on both sides of the border.
Another crucial challenge is “Vaccine-derived” poliovirus transfer. This stems from the oral polio vaccinewhich is still used in some regions and uses a live but weakened poliovirus.
This in itself would not cause any problems, but if immunization rates in a population are low, the vaccine strain can circulate and change genetically over time, rarely causing paralysis, such as with wild polio.
“Every case is a concern,” McInally said. “But once we can eliminate the wild virus, vaccine-induced cases will disappear relatively quickly.”
O’Leary notes that in 1988, when the GPEI started, there were 1,000 cases of polio per day in 125 countries. He compares the polio program to running a marathon – with just a few hundred meters to go. Still, he remained cautious: “Eradication is a zero-sum game. We have to be very clear: if we look back and everything is zero, we can say it’s great.”