One by one the children opened their mouths to receive two drops of polio vaccine, holding out their hand to get their ‘purple pinky’ – one finger painted with indelible purple ink to show they had been immunised.

“Some of them tried to suck off the ink because they wanted another toy as a reward,” recalls Ann Barrett. “Their faces lit up; they’d never had anything like that before.”

Ann, from Gomersal, recently travelled to the south Indian region of Chennai with members of Rotary and Inner Wheel clubs from across the district, to help local health workers immunise thousands of under-fives against polio.

Rotary International pledged to eradicate polio from the world back in 1985, when there were 125 endemic countries. Now there are four; Afghanistan, India, Pakistan and Nigeria.

Thanks to work carried out by Rotary International, Unicef and other organisations, two billion children have been protected from polio.

According to Rotary, India has had no new reported cases of polio since January 2011, but to be considered polio-free there have to be no new cases for three years.

“The fight isn’t over yet, but we’re optimistic it can be eradicated,” says Ann, a member of Cleckheaton Inner Wheel, whose partner, former Lord Mayor of Bradford Allan Hillary, is in Idle and Greengates Rotary Club.

“We hope the World Health Organisation can declare India polio-free in two years.”

Ann travelled to remote areas and, along with Rotarians from Bingley and Mirfield clubs, helped to administer vaccines in a little village school.

“The schoolroom was very basic with just a small blackboard and a couple of benches. There was nothing to show that the children had any games to play with,” says Ann.

“But even though they had nothing, they all had wonderful smiles on their faces. They played cricket with us, using a couple of stones and a banana twig for a bat.”

A long queue snaked around the school, mostly parents or older siblings bringing babies and young children.

“Two drops of polio vaccine was dropped on their tongue, then ink was painted on their little fingers to show who’d been immunised. This was followed up by house-to-house visits to check that all under-fives, who are most vulnerable, are vaccinated,” says Ann, who gave the children small gifts, such as toy cars donated by Idle and Greengates Rotary Club and more than 60 cuddly toys donated by Jill Kemp, managing director of Care Recruitment Specialists Ltd in Little Germany.

A former nurse, who worked at Bradford Royal Infirmary and St Luke’s Hospital, Ann saw at firsthand the devastating effects of polio.

“I saw people with wasted limbs moving about on self-made carts, and people sleeping on roadsides. People would come up and stroke our arms. The poverty really hits you. It was a big shock at first. It made me realise how much we take for granted in the UK,” she says.

“Houses in the village were very basic; with just two rooms. People were doing piece work in their homes on looms held together with string.

“The southern end of India was hit by the 2004 South Asian tsunami, and because it’s such a poor area, it hasn’t recovered. We saw houses with makeshift tin roofs, and families sleeping in cars.”

As well as suffering physical disabilities, those afflicted with polio face a social stigma and often drop out of school early.

Ann was accompanied by John and Chris Philips from Mirfield Rotary who have been to India several times. Chris, the Yorkshire Rotary polio officer, said: “I saw two men who had contracted polio as infants, hobbling around begging on pencil thin legs at a bus stand close to where John and I were manning a desk doubling as a ‘polio booth’ in the middle of a noisy, hot, dusty, chaotic traffic nerve centre.

“As buses loaded with 40 to 50 passengers arrived every couple of minutes, we looked out for babies and infants so we could give them two drops of the life-saving vaccine.”

Chris says the mission to eradicate polio from India looks promising. “The local director of public health is optimistic too. When he thanked us for coming he told us: ‘Your team has helped boost staff morale here significantly and I believe we are at the end game’.”

Rotary clubs in Britain and Ireland have donated more than £16.5 million to polio immunisation initiatives. The money goes towards funding national immunisation drives for all children under age five in endemic and high-risk countries, as well as taking measures to control outbreaks and improving public health infrastructures.

India used to be the epicentre of polio. In 1985, there were an estimated 150,000 cases there and as recently as 2009 there were 741, more than any other country in the world.

Thousands of impromptu vaccination booths have been set up across India, and regular immunisation days aim to reach more than 170 million under fives.

“Rotary does a lot of good work around the world,” says Ann. “They’ve been trying to eradicate polio for 20 years and next year may be the last time they’re needed. I found it a very rewarding experience – one I’ll never forget.”

Actor Ewan McGregor has travelled to India as part of a mission to immunise some of the world’s hardest-to-reach children.

In BBC TV programme Cold Chain Mission, viewers this week saw Ewan and his team deliver vaccines so fragile they must be kept constantly cold as they are passed along the supply chain, from freezer to freezer. The routes these vaccines travel are known as cold chains, and a vast network exists across the globe.

In this series, Ewan is following three of the world’s toughest cold chains, supported by Unicef.

In the first episode, shown on Sunday, Ewan, a Unicef ambassador, followed a route through India in a race against time to stop polio spreading.

The next programme is on Sunday on BBC2 at 9pm.