Although the world is close to wiping out polio, there are signs the virus is not quite ready to go the way of smallpox – the only disease eradicated by humans – with two countries seeing an increase in cases caused by the wild polio virus that can cause paralysis and even death, particularly in infants and children.
Now, the cuts in USAID contracts that support polio vaccination have raised concern that other countries will see a resurgence, too, reports NPR.
Even with in-country vaccination campaigns and global aid, Pakistan and Afghanistan have so far been unable to stop transmission of the disease. In 2024, Pakistan’s numbers spiked to 74 while Afghanistan saw 24 recorded polio cases. So far this year, Pakistan has reported six cases and Afghanistan, one.
These new cases are tied to disruptions in ongoing vaccine campaigns, while global health officials are concerned those numbers could balloon, and that polio could re-emerge in other countries as well in the wake of the dismantling of USAID.
In a series of memos drafted by Nicholas Enrich, acting Assistant Administrator for Global Health at USAID, and obtained by the press, the potential for damage is quantified with estimates of how many people would possibly become sick and die if the US aid pause continues.
Enrich projected an additional 200 000 cases of polio that cause paralysis each year, and hundreds of millions of infections overall.
In Afghanistan and Pakistan, while the numbers are relatively low, the question is: why does the wild virus persist in these two countries when it’s been eradicated from elsewhere since 2020? (Other countries have experienced cases of vaccine-derived polio, which can occur when the weakened virus in the oral vaccine mutates and regains its ability to cause paralysis).
Why Pakistan is seeing a resurgence
Usman Ali, a two-year-old, is one of 74 children in five Pakistani provinces to have contracted polio in 2024. He is now experiencing partial paralysis.
Ali lives in Balochistan province, bordering Afghanistan. When polio workers came door-to-door in April 2024 in his simple village, he had a fever. His parents worried the vaccine would worsen his illness, so they refused it.
They asked polio workers to mark his finger with purple ink anyway to make it look as if he’d been vaccinated.
Ali had fevers on and off for several weeks, and in June, began having trouble walking. His parents took him to a private clinic.
When a later test of his stool sample came back positive for polio, they realised it was paralysis and could be permanent. Since then, Ali has recovered somewhat but still has partial paralysis in one leg.
His community comprises seasonal migrants who travel yearly to herd their sheep, mostly in neighbouring Punjab province. Their village lacks toilets and sanitation, and people defecate in the open, which health officials say puts around 2 000 other children at risk of contracting polio – which can be spread by contact with human waste.
“This is a vulnerable community. They can easily carry the virus from one place to another place,” says Saeedullah Lawoon, a local polio community communication officer.
Polio has surged despite Pakistan’s extensive surveillance programme and repeated door-to-door vaccination campaigns. The country has also struggled to maintain the necessary high rates of immunisation while combating vaccine fatigue.
To be optimally protected from polio, experts recommend Pakistani children receive two doses of the injectable vaccine and at least three doses of the oral – an aggressive course aimed at interrupting transmission.
In 2023, only 84% of the country’s eligible children received two doses of the injectable vaccine, indicate WHO and Unicef estimates shared by the Pakistan Polio Programme, while 86% of children received three doses of the oral vaccine during routine immunisation.
Vaccination rates during door-to-door drives can surpass 90%, according to Pakistan Polio Programme data, but these campaigns only offer the oral vaccine.
To receive the injectable vaccine, parents must travel to designated facilities. The injectable vaccine is harder to administer and requires trained health workers and sanitary conditions.
The result is that some children only receive the oral vaccine, while some aren’t vaccinated at all.
More than half of the polio cases in Pakistan last year were from children who hadn’t received a single dose of either version of the vaccines. The other 45% were children who had received the vaccine, sometimes up to seven times, according to case data.
Experts say receiving that many doses is not dangerous for a child. Pakistan’s Polio Programme says what’s important is that every child is vaccinated during each vaccine campaign to maintain their immunity.
The polio eradication programme was started in 1994 and originally helped to significantly reduce the number of polio cases in the country, which used to be in the tens of thousands. Between 1994 and 2013, the average number of annual cases was reduced by around 96%, from 2 635 to 93.
Case numbers seesawed in the following years before reaching an all-time low in 2021, when Pakistan recorded only one infection.
Although cases have fluctuated in the past, experts say last year's increase was particularly alarming.
Zulfiqar Bhutta, founding director of The Institute for Global Health and Development at Karachi’s Aga Khan University, says there isn’t one single factor leading to polio exacerbations in Pakistan. It’s always a combination.
He attributes the spike partly to laxity with door-to-door vaccination campaigns. In some cases, parents or health workers will mark the finger of a child who hasn’t been vaccinated, which he attributes to fatigue among health workers under pressure to hit vaccination targets and exhausted from dealing with uncooperative parents. He also cites inadequate supervision of healthcare workers.
Then there's vaccine distrust – still a problem in parts of Pakistan and neighbouring Afghanistan. Some think the vaccine will affect fertility, others believe they’re part of a Western conspiracy.
Polio workers also struggle to access certain areas because of conflict and security risks. In the past decade, they’ve become the target of militant groups who accuse them of being government spies or agents of the West.
In some cases, parents refuse vaccines for their children because they’ve grown tired of repeat visits by polio workers, who are required to give oral polio drops during each vaccination campaign to every child under five – including those who’ve received them multiple times before.
According to a September 2024 report by the Independent Monitoring Board of the Global Polio Eradication Initiative, more than 4m Pakistani children missed being vaccinated last year.
Previously, both Afghanistan and Pakistan have each come close to eradicating the virus, says Dr Hamid Jafari, the WHO director of polio eradication for the region.
But the two nations’ vaccine campaigns didn’t align, so pockets of infection can persist and spread between the countries.
“Polio is an epidemic-prone disease – if you don’t interrupt transmission, it resurges after every few years.”
Numerous recent cases involve children who avoided severe paralysis, thanks to some level of protection from oral vaccines, says Zia Ur Rehman, spokesperson for the Pakistan Polio Eradication Programme, which is “very encouraging, and shows there is always a benefit of repeated vaccination”.
Pakistan held its first vaccination drive of the year in February efforts to ensure all under-fives have received at least one dose of the oral vaccine, with the goal of eventually achieving herd immunity. This should occur with polio when around 80% of the population is vaccinated, although Pakistan presents a special challenge.
There’s no clear threshold for herd immunity in Pakistan, says the WHO’s Hamid Jafari. “There isn’t just one figure we can go with in what level of immunity you need to stop transmission.”
He said the 80% rate might be an average figure for countries with better sanitation and less population density, but in South Asia, higher vaccination rates are needed to interrupt transmission.
The campaign aimed to reach about 45m children around the country, but according to the Polio Programme, workers vaccinated about 200 000 fewer children than the target, though it’s difficult to verify.
The number of children who didn’t receive the vaccine because family refused was around 66 000, show Pakistan Polio Programme data.
The next vaccination campaign takes place this month.
Meanwhile, the virus has been detected in sewage samples around Pakistan, including in Punjab province, home to around half of the country’s children. Before a case was confirmed there last year, the province had been without a case of polio since 2020.
Punjab has had one polio case in 2025.
Bhutta said the widespread circulation of the virus means the situation could quickly spiral into something much worse.
“This is like sitting on top of a volcano. This can erupt anytime.”
Changes in strategy leave some children behind
A few months ago, an Afghan businessman named Mohammad noticed his youngest son’s hand looked extremely thin and was bending at an unnatural angle. Several tests later, he and his wife’s worst fears were confirmed: “We were told he was infected with the polio virus,” he said. “We missed his vaccines. Now a part of his hand is paralysed.”
Mohammad, who requested his full name be withheld, fearing reprisal, blames his son’s condition on the Taliban’s decision to suspend door-to-door vaccination campaigns in August 2024.
No official reason was provided; health workers said the ban was a result of suspicion of Western aid and the Taliban’s restrictions placed on women workers, who can’t travel without a male legal guardian.
“They stopped the health workers from coming to the communities, and instead moved the vaccinations to mosques,” Mohammad says.
Mohammad, who has four other children who are vaccinated and healthy, says that campaign suspensions coupled with the Taliban restrictions made it hard for his family to get the children vaccinated.
“I travel a lot for work, and the women in the family can’t just walk to the local mosque to get vaccines,” he says, referring to the Taliban’s ban on women’s movement.
Although the number of polio cases in Afghanistan is significantly less than in Pakistan, the spike was “extremely high” in 2024, say officials: 24 cases compared with just six the previous year.
“The main reason is the poor quality of campaigns, particularly the lack of the house-to-house distribution system which has been successful in the past,” says one health official who requested anonymity.
The spread is alarming, he says.
While Pakistan and Afghanistan remain the only countries that have failed to eliminate the polio virus, Afghanistan had made some progress in reducing cases in recent years.
However, Taliban groups have long held suspicions that the door-to-door vaccination programmes involving Western aid might be used to spy on communities.
So for many years during its war with the US forces in Afghanistan, the Taliban refused to allow immunisation campaigns in areas they controlled. When the Taliban took over Afghanistan after the American withdrawal in 2021, health workers had hoped they could finally be allowed access to previously unreachable regions, however, the Taliban expanded their ban even further.
Vaccination drives have also been hampered by the Taliban’s successive bans on women’s employment across various sectors, including in NGOs and development work.
“Women are crucial to such campaigns because in a conservative country like Afghanistan they are more welcome by families and communities with women and children, and which allows them to not only provide vaccines and raise awareness but is also crucial to reporting cases,” said the health official.
Instead, he says, the remaining, mostly male, health workers have been advised by the Taliban to conduct campaigns in mosques, where families are expected to take their children for the jabs.
“This leaves many children unvaccinated since most families aren’t aware or proactive about getting vaccines,” he says, adding that for the vaccines to be successful, at least 95% of children under the five need to be covered during each campaign.
According to UN estimates, more than half the Afghan population relied on humanitarian assistance in 2024 from charities like the UN’s World Food Programme.
And in densely packed areas with limited sanitation, many children are already struggling with health issues that make them more vulnerable to polio.
“Immunity among children is low and there are other diseases like diarrhoea and malnutrition, which alongside a lack of hygiene and sanitation, make it a deadly combination,” he says.
Afghan health workers are continuing to advocate, with international organisations, to resume door-to-door campaigns, and meanwhile, healthcare workers are encouraging parents to take their children to local vaccination centres.
For Mohammad’s son, though, it might already be too late.
NPR article – Could polio be poised for a comeback? (Open access)
See more from MedicalBrief archives:
Path that led to a potential polio resurgence
Polio may never be eradicated, say experts
Gavi green-lights new jab in global fight against polio
Polio virus discovery shows we can't let guard down