In this two-parter, Ewan McGregor is on a mission to the ends of the earth to immunise some of the hardest-to-reach children in the world. Against the odds, Ewan and his team deliver vaccines to the world's most remote children as health workers do every day. But their fragile nature means the vaccines must be kept constantly cold as they are passed along the supply chain, from freezer to freezer - wherever that may be. The routes these vaccines travel are known as cold chains, and a vast network of them exists across the globe. In this series Ewan is following three of the world's toughest cold chains, supported by Unicef, who immunise over half of the world's children.

In the first episode Ewan, who has been a Unicef ambassador for eight years, follows a route that takes him through India. In a country with a booming population, often on the move, the cold chain is a race against time to stop polio before it can enter the country and spread. From India, Ewan continues his journey into the isolated wilderness of Nepal. He must endure a gruelling two-day trek to reach a tiny community secluded high in the Himalayas, but not before attempting to land at one of the world's most dangerous airstrips.

These two programmes give Ewan an opportunity to go to three very different countries, three situations, and find out just how much it takes to save children's lives.

Ewan said of his experience: 'The cold chain routes these vaccines follow can be hugely challenging and adventurous, and I was keen to explore some of them to discover how they reach the world's most remote children.'. Show less