Richard Phinney becomes the first journalist to visit Dr Peter Aaby in his field site at the Bandim Health Project, where a team of Danish and African scientists have toiled doggedly for more than 30 years - through civil wars, natural disasters and epidemics.
A small army of doctors, nurses, field workers and lab technicians now monitor the health of 100,000 people - or 12% of all children.
It's an extraordinary task in a country with a government so weak it collects no taxes and keeps hardly any records.
The results of this work – more than 600 scholarly articles in the world's leading medical journals – has expanded our understanding of how the most devastating childhood infections spread.
In the 1990s, data from the project was even responsible for the withdrawal of a potentially deadly measles vaccine by the World Health Organisation.
However Aaby's most explosive findings have been ignored by the WHO. They show that vaccines and vitamin supplements have long term unintended consequences - some good and some bad - on the immune system of young children. And in the most alarming cases, girls fare much worse than boys.
The results challenge WHO's global health advice, followed by most countries in the developing world, and could mean that thousands of young lives, in Africa and beyond, are needlessly at risk.