Marsh initiated his research career at the Medical Research Council Unit in the Gambia, where he worked on the immunology of malaria. From 1985 till 1989, he was at the Institute of Molecular Medicine in Oxford. In 1989, he, along with his colleagues, established a series of research projects on the immunology and clinical epidemiology of malaria at Kilifi on the coast of Kenya; these developed into an international programme, the KEMRI
Wellcome Trust Research Programme, which he directed until 2014. Marsh has been a professor of Tropical Medicine in Nuffield Department of Medicine at the University of Oxford since 1994 and is currently Director of Africa Oxford Initiative. Since 2014 Marsh has been senior adviser at the African Academy of sciences, based at their headquarters in Nairobi, where he worked with colleagues to develop the Alliance for Accelerating Excellence in Science in Africa (AESA), a platform aiming to shift the centre of gravity of research to the African continent. He currently co leads the AAS Covid programme which has worked closely with AUDA NEPAD, Africa CDC and WHO Afro to develop COVID-19 research priorities for the continent. ==Research==