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Professor Tom Harrison

Professor of Infectious Diseases
Deputy Director and Lead, Centre for Global Health, Institute of Infection and Immunity.

Tom Harrison is Professor of Infectious Diseases and Medicine, Deputy Director of the Institute for Infection and Immunity, and Lead for the Centre of Global Health. He is also Honorary Consultant at St Georges University Hospitals NHS Foundation Trust.

He leads a clinical and laboratory research programme on the prevention and treatment of cryptococcal meningitis with colleagues from St George’s, and in collaboration with other UK institutions, and colleagues across study sites in Sub-Saharan Africa. As a member of the InterTB consortium, he is also involved in phase II and III clinical trials aimed at simplifying and reducing the duration of treatment for pulmonary tuberculosis through the use of high dose rifamycins, and leads the hospital multi-drug resistant (MDR) TB service and research programme.

Professor Harrison studied Natural Sciences at Christ’s College Cambridge before studying Medicine at St Georges and then training in Infectious Diseases in London and Boston, USA. In Boston, funded by an NIH/Fogarty Award and an Infectious Diseases Society of America (IDSA) Fellowship, he trained in the laboratory of Stuart Levitz investigating host defense against Cryptococcus neoformans, the commonest cause of meningitis in Africa, and responsible for an estimated 180,000 deaths per year and 10-20% of all HIV-related deaths.

On returning to the UK in 1997, he obtained an Advanced Training Fellowship from The Wellcome Trust, and set up a series of ongoing clinical studies, first in Thailand and subsequently through a network of collaborating centres across Sub-Saharan Africa. Laboratory work focuses on host immunity and novel immunotherapeutic approaches and understanding pathogen virulence and evolution. In addition, with Dr Amina Jindani, he is helping drive clinical studies to simplify and shorten the treatment of tuberculosis; and leads the hospital service and a research programme on multi-drug resistant TB.

He continues to work as a hospital consultant in the Infectious Diseases Department, and remains actively involved in the clinical and academic supervision of trainees in Infectious diseases from across London.

Professor Harrison has served on guidelines panels for WHO, IDSA, and the Southern African HIV Clinicians Society. He was a member of the MRC Infection and Immunity Board from 2014-18, and has served on many MRC panels in Global Health. He is an Adjunct Member at The Institute of Infectious Diseases and Molecular Medicine, University of Cape Town



Professor Harrison’s main research focus addresses the pathophysiology, immunology, management, and prevention of cryptococcal meningitis. In the first study of its kind, in Thailand, using serial quantitative cultures of cerebrospinal fluid, the fungicidal activities of different drug treatments for cryptococcal meningitis were directly compared using the rate of clearance of infection. The technique was shown to be much more powerful than prior markers of response, opening the way for more rapid assessment of novel treatments. A series of follow-up phase II trials were completed in centres in Africa, which led to the landmark, MRC-funded, phase III ACTA trial. The regimens studied in ACTA were associated with improved survival, have led to rapid revision of WHO guidelines, and are driving world-wide access to flucytosine one of the key antifungal drugs involved.

Current studies are examining use of liposomal amphotericin, which is better tolerated than conventional amphotericin B. A large phase III trial is ongoing, comparing a single high dose of liposomal amphotericin, plus fluconazole and flucytosine, against the new (based on ACTA) WHO standard of one-week of amphotericin B plus flucytosine.

A pivotal early study demonstrated the value of cryptococcal antigen (CrAg) detection in blood as a very sensitive and specific screening tool to identify those HIV-infected patients at risk of developing clinical cryptococcal meningitis. A point of care test to enable screening was jointly developed and tested with collaborators from Nevada and industry, and screening protocols developed. This test and pre-emptive treatment strategy was shown, together with antiretroviral adherence support, to lead to a 28% reduction in one year mortality in a phase III trial (REMSTART) in patients presenting with late stage HIV infection.

Laboratory projects, built around the clinical studies, examine the effects of pathogen variation and host immunity on the outcome of cryptococcal infection, with the aim of developing novel management strategies.

With Dr Amina Jindani, Professor Harrison is also helping drive studies to simplify and reduce the duration of therapy for tuberculosis through the use of high dose rifamycins. A major phase III trial (RIFAQUIN) demonstrated for the first time that a once weekly continuation phase regimen, based on high dose rifapentine and moxifloxacin, was equivalent to standard short course chemotherapy. The ongoing RIFASHORT trial is testing high dose rifampicin (1200 mg and 1800 mg/d) in 4 month regimens versus the stadard 6 month regimen.

Current Grants

  1. EDCTP. (Co-PI with Jarvis). High Dose AMBISOME on a Fluconazole Backbone for Cryptococcal Meningitis Induction Therapy in sub-Saharan Africa: A Randomized Controlled Trial. Value 9.999 million Euros. Jan 2017- Dec 2020
  2. MRC/DFID/WT Global Health Trials. Co-applicant, (PI Jindani): RIFASHORT. A randomized trial to evaluate the toxicity and efficacy of 1200mg and 1800mg rifampicin daily for 4 months in the treatment of pulmonary tuberculosis. 2015-2021. £2.3 million. Additional £814,000 awarded 2019 (led application for additional funds).
  3. EDCTP. Co-applicant (PI Angela Loyse). Integrating the diagnosis and management of HIV-associated central nervous system (CNS) infections into routine health services in low and middle income countries (LMICs). 2016-2020. 1.88 million Euros
  4. Wellcome Trust. Co-Applicant. Clinical PhD Programme in Global Health with LSHTM, UCL, Barts, Kings and Brighton and Sussex Med School. 2017-2021.


Professor Harrison is involved in undergraduate and post-graduate teaching and training in Infectious Diseases and Global Health. He lecturers regularly on the intercalated BSc/BSc Global Health Diseases Module; and widely at national and international meetings. For some years he led the South London Infectious Disease Training programme, and still leads the academic training in Infection at St Georges.

He has supervised as primary or co-supervisor 10 PhD students and 5 MD (Res) students to completion. Many of these students continue in successful academic careers and several have joined the group at St George’s or continue to collaborate, based in other institutions.

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