This two-part documentary takes us inside the world's most remarkable health surveillance unit, in the impoverished West African country of Guinea Bissau, where a team of Danish and African medical researchers are piecing together evidence that could change public healthcare forever. The results challenge the UN's global health advice which is followed by most countries in the developing world. The findings which show that vaccines and vitamin supplements have long-term unintended consequences - some good and some bad - on the immune system of young children.