evidence: The aim of the UN-backed COVAX scheme is to get two billion vaccine doses into the arms of around a quarter of the population of poorer countries by the end of 2021. What are the main challenges that need to be overcome, if this historic global effort is to be achieved? [...] "WHO supports countries in their efforts to acquire and sustain vaccine production technology and capacity", says Diane Abad-Vergara, COVAX communications lead for the agency, "through such initiatives as the Developing Countries Vaccine Manufacturers Network, and helps them to build additional manufacturing bases — especially in Africa, Asia, and Latin America — which will be essential to meeting ongoing demand for COVID-19 booster shots and future vaccines.