Joy has lived and worked in East, West and Southern Africa, including  as a clinical lecturer and neonatalogist in Ghana in the 1990s. She shifted to public health and global estimation working at the WHO Collaborating Center, CDC Atlanta, USA (1998-2001), and then at the Institute of Child Health, London, UK (2001-2004), completing a Masters of Public Health at Emory University, Atlanta and a PhD in perinatal epidemiology at University College London, UK. For ten years she was Director Global Evidence and Policy for Saving Newborn Lives (SNL) at Save the Children, funded by The Bill & Melinda Gates Foundation. She has working with governments and partners to scale up and evaluate newborn care including leadership in Lancet Every Newborn series and Action Plan, leading to the first SDG on neonatal survival.

Joy joined LSHTM in 2013 and has been Director or Co-Director of the MARCH Centre, and helped to build diverse teams, and expand funding for research on newborn health and stillbirths. She has been appointed to the UK Academies of Medical Science and the US National Academies of Medicine, and been awarded sveral global prizes. 

She has published over 320 peer reviewed papers (H index >110), as well as a range of chapters, books and policy relevant reports. She co-led several Lancet series on newborn survival and stillbirths. She is currently co-chair for The Lancet Commission on Implementation and Evidence.