Marie-Louise Newell is Director of the Africa Centre and Professor of Paediatric Epidemiology at University College London. She is an infectious disease epidemiologist who has made important contributions to our understanding of the transmission of HIV from mothers to their children. Her work has informed national and international policies contributing to the substantial decline in vertically-acquired HIV infection by preventing infection of children during pregnancy and delivery. She has ensured translation of research into policy and practice as a member and chair of international expert groups in the UK, Europe, Africa and for the World Health Organization.