Trundling across the Afghan-Pakistani border in a handcart, Shayma dismisses militant threats and conspiracy theories about polio vaccinators while her four children receive drops that could finally eradicate the crippling disease.
About 1.3 million oral vaccinations are administered every year to children at the Torkham Gate crossing, the focal point of an intense global campaign to eradicate polio by 2018.
But Afghanistan and Pakistan—two of the three remaining "endemic" polio nations—face a tough task due to fighting on either side of the border, Taliban opposition to vaccinations and rumours that the drops could cause impotency.
Families hurrying through the Torkham mountain pass are diverted down a channel where health workers deftly deliver two liquid drops into the mouths of all children aged under five.
"We want the vaccinations so that my children don't become disabled," Shayma told AFP from behind an all-enveloping blue burqa as she headed home from Peshawar in Pakistan to the Afghan city of Jalalabad.
"It is not true that the vaccination is bad. I don't agree with this," she said. "I believe it stops polio."
Pakistan is a major concern for anti-polio experts with 93 cases last year, up from 58 in 2012.
Vaccinators have been shot dead, bombed or taken hostage in Peshawar, Karachi and elsewhere, and some anti-polio programmes have been suspended.
Twelve people were killed and 11 injured when three roadside bombs targeting a polio vaccination team in Pakistan's restive northwest exploded Saturday.
The Pakistan Taliban oppose immunisation, saying it is a cover for US spying, and some people believe it is also a plot to poison Muslim children and cause infertility.
While Afghanistan has had notable success in tackling polio, with 80 cases in 2011 and just 14 in 2013, eradication may be a long way off due to the constant flood of people back and forth across the porous border.
Some families refuse vaccine
"It does pose a big challenge in trying to ensure each and every child is vaccinated every single time," UNICEF spokesman Kshitij Joshi said.
"Afghanistan and Pakistan are same epidemiological block and it is important that children on either side of the border are vaccinated to ensure absolute protection."
Vaccinated children are marked on the thumb with a pen that lasts one month, but catching every child is nearly impossible in the crush of people on the colonial-era frontier, which is not officially recognised by Afghanistan.
The vaccine is voluntary and is rejected by some families. One elderly man shouted at health workers and refused to allow his child to receive drops.
"Sometimes we find a person like this, but the majority of people know that it is good," said vaccination supervisor Asifullah who, like many Afghans, only uses one name.
In Jalalabad city, on the main road to Kabul, UNICEF also targets migrant communities who move regularly between the two countries in search of work.
One father living in a makeshift tent said he had been told that the drops had a bad effect and would make his children "naughty".
After a discussion, UNICEF female coordinator Rana persuaded him to allow his family to receive the vaccine.
Female volunteers are crucial to the anti-polio campaign as they are able to enter private homes, but they can't access more dangerous areas in the Afghan border region.
"It is difficult for women to go to several districts," said Rana. "We are not allowed as the security is not good."
Taliban militants in southern Afghanistan generally support vaccination—a result, says UNICEF, of years of work ensuring that the programme is seen as strictly neutral.
But in Pakistan and some parts of eastern Afghanistan, the Taliban have stopped vaccinators reaching children in key polio enclaves.
"The Taliban in Kunar and Nangarhar provinces oppose the vaccinations, so we have 20,000 children there who have been unvaccinated for several months," Faizullah Kakar, the Afghan president's polio specialist, told AFP.
"These places are near Kabul, so we are very nervous that if it gets to the capital it could spread quickly."
The risk was highlighted last month when Kabul recorded its first polio case since 2001 after a three-year-old girl was diagnosed, probably due to her father carrying the disease from Pakistan.
Tackling 'Taliban propaganda'
"The problem is firstly the Taliban, but it is also refugees in Kunar who are somehow convinced that vaccinations are not good for their children and they also tell local Afghans not to vaccinate," said Kakar.
"We stopped three FM radio stations from constantly broadcasting propaganda against the polio campaign.
"And we try to halt books circulating that pick bits of science and claim that vaccines are from pig products or cause infertility.
"The Taliban use how Osama bin Laden was found (in part through a fake vaccination programme), so they say it is about spying."
Worldwide, polio is now restricted to two endemic areas—the Afghan-Pakistan border and northern Nigeria.
But unless vaccination at key points such as Torkham Gate succeeds in stamping polio out completely, the risk of outbreaks in other countries will always remain.
For Kakar, there is one main obstacle to ridding the world of a highly contagious disease that easily preventable but impossible to cure.
"If we have peace here, we would hope to end polio very soon," he said. "Without peace, it is a lot more uncertain."