FRANSESCO GUARASCIO THE global scheme to deliver COVID-19 vaccines to poorer countries faces a "very high" risk of failure, potentially leaving nations home to billions of people with no access to vaccines until as late as 2024, internal documents say. The World Health Organization's COVAX programme is the main global scheme to vaccinate people in poor and middle-income countries around the world against the coronavirus. It aims to deliver at least 2 billion vaccine doses by the end of 2021 to cover 20% of the most vulnerable people in 91 poor and middle-income countries, mostly in Africa, Asia and Latin…