Jimmy is a physician, qualifying from Liverpool University in 1979, and specialises in infectious diseases, epidemiology and public health. Previous roles include working in The Gambia for Save the Children Fund, and in Bo, Sierra Leone for the Medical Research Council, where he worked on ivermectin for onchocerciasis from 1986-1990. He was Team Leader for the Medical Research Council Programme on AIDS, based at the Uganda Virus Research Institute in Entebbe, from 1995 until 2002. Jimmy has been an academic staff member at both the Liverpool School of Tropical Medicine and the London School of Hygiene and Tropical Medicine, where he was Professor of International Public Health from 1999-2004.
Previously Jimmy was Head of International Activities (2004-2013), and Population Health (2013-2015), at the Wellcome Trust where he was responsible for strategy, policy and developing the scientific portfolio for research on population science and public health research in the UK and in low and middle income countries.
He returned to LSHTM in 2015 and worked to create the UK Public Health Rapid Support Team, which is funded by the UK Government. He stepped down as the deputy director in 2019.
Jimmy is a member of the Scientific Advisory Committee for WHO's R&D Blueprint for Action to Prevent Epidemics, a committee member of the Global Co-ordination Mechanism for R&D, a Trustee for the Royal Society for Tropical Medicine and Hygiene and DTM&H examiner for the Royal College of Physicians. He chairs the Scientific Advisory Group for Research for Health in Humanitarian Crises (R2HC) and is chair of the Ebola Biobank Governance Group for Public Health England.