Imperial College London

ProfessorTimothyHallett

Faculty of MedicineSchool of Public Health

Professor of Global Health
 
 
 
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Contact

 

+44 (0)20 7594 1150timothy.hallett

 
 
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Location

 

Norfolk PlaceSt Mary's Campus

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Summary

 

Publications

Publication Type
Year
to

195 results found

Heffernan A, Cooke GS, Nayagam S, Thursz M, Hallett TBet al., 2019, Scaling up prevention and treatment towards the elimination of hepatitis C: a global mathematical model., Lancet

BACKGROUND: The revolution in hepatitis C virus (HCV) treatment through the development of direct-acting antivirals (DAAs) has generated international interest in the global elimination of the disease as a public health threat. In 2017, this led WHO to establish elimination targets for 2030. We evaluated the impact of public health interventions on the global HCV epidemic and investigated whether WHO's elimination targets could be met. METHODS: We developed a dynamic transmission model of the global HCV epidemic, calibrated to 190 countries, which incorporates data on demography, people who inject drugs (PWID), current coverage of treatment and prevention programmes, natural history of the disease, HCV prevalence, and HCV-attributable mortality. We estimated the worldwide impact of scaling up interventions that reduce risk of transmission, improve access to treatment, and increase screening for HCV infection by considering six scenarios: no change made to existing levels of diagnosis or treatment; sequentially adding the following interventions: blood safety and infection control, PWID harm reduction, offering of DAAs at diagnosis, and outreach screening to increase the number diagnosed; and a scenario in which DAAs are not introduced (ie, treatment is only with pegylated interferon and oral ribavirin) to investigate the effect of DAA use. We explored the effect of varying the coverage or impact of these interventions in sensitivity analyses and also assessed the impact on the global epidemic of removing certain key countries from the package of interventions. FINDINGS: By 2030, interventions that reduce risk of transmission in the non-PWID population by 80% and increase coverage of harm reduction services to 40% of PWID could avert 14·1 million (95% credible interval 13·0-15·2) new infections. Offering DAAs at time of diagnosis in all countries could prevent 640 000 deaths (620 000-670 000) from cirrhosis and liver cancer. A comprehensive packa

JOURNAL ARTICLE

Bórquez A, Guanira JV, Revill P, Caballero P, Silva-Santisteban A, Kelly S, Salazar X, Bracamonte P, Minaya P, Hallett TB, Cáceres CFet al., 2019, The impact and cost-effectiveness of combined HIV prevention scenarios among transgender women sex-workers in Lima, Peru: a mathematical modelling study., Lancet Public Health

BACKGROUND: HIV incidence remains high among transgender women in Lima, Peru, most of whom report sex work. On the basis of a stakeholder analysis and health system capacity assessment, we designed a mathematical model to guide HIV programmatic planning among transgender women sex workers (TWSW) in Lima. METHODS: Using a deterministic compartmental model, we modelled HIV transmission among TWSW, their stable partners, and their clients to estimate the impact and cost-effectiveness of combinations of interventions compared with the standard of care on reducing HIV incidence over a 10-year period. We simulated HIV transmission accounting for differences in sexual positioning in anal intercourse and condom use by partner type and fitted the model to HIV surveillance data using Latin hypercube sampling. The interventions we considered were 15% relative increase in condom use with clients and 10% relative increase with stable partners; increase in antiretroviral treatment (ART) coverage at CD4 count lower than 500 cells per mm3 and greater than or equal to 500 cells per mm3; and 15% pre-exposure prophylaxis (PrEP) coverage using generic and branded formulations. We considered a basic scenario accounting for current limitations in the Peruvian HIV services and an enhanced scenario assuming achievement of the UNAIDS 90-90-90 targets and general improvements in HIV services. The 50 best fits according to log-likelihood were used to give the minimum and maximum values of intervention effect for each combination. We used disability-adjusted life-years (DALYs) to measure the negative health outcomes associated with HIV infection that could be averted through the interventions investigated and calculated incremental cost-effectiveness ratios to compare their cost-effectiveness. FINDINGS: Under the basic scenario, combining the four interventions of increasing condom use with clients and stable partners, extending ART to people with CD4 count greater than or equal to 500 cells p

JOURNAL ARTICLE

Stopard IJ, Mcgillen JB, Hauck K, Hallett TBet al., 2019, The influence of constraints on the efficient allocation of resources for HIV prevention: a modelling study., AIDS

OBJECTIVE: To investigate how 'real-world' constraints on the allocative and technical efficiency of HIV prevention programmes affect resource allocation and the number of infections averted. DESIGN: Epidemiological modelling and economic analyses in Benin, South Africa and Tanzania. METHODS: We simulated different HIV prevention programmes, and first determined the most efficient allocation of resources, in which the HIV prevention budget is shared between specific interventions, risk-groups and provinces to maximise the number of infections averted. We then identified the efficient allocation of resources and achievable impact given constraints to allocative efficiency: earmarking (provinces with budgets fund PrEP for low-risk women first), meeting treatment targets (provinces with budgets fund UTT first) and minimizing changes in the geographical distribution of funds. We modelled technical inefficiencies as a reduction in the coverage of PrEP or UTT, which were factored into the resource allocation process or took effect following the allocation. Each scenario was investigated over a range of budgets, such that the impact reaches its maximum. RESULTS: The 'earmarking', 'meeting targets' and 'minimizing change' constraints reduce the potential impact of HIV prevention programmes, but at the higher budgets these constraints have little to no effect (approximately 35 billion US$ in Tanzania). Over-estimating technical efficiencies results in a loss of impact compared to what would be possible if technical efficiencies were known accurately. CONCLUSIONS: Failing to account for constraints on allocative and technical efficiency can result in the overestimation of the health gains possible, and for technical inefficiencies the allocation of an inefficient strategy.

JOURNAL ARTICLE

Schaefer R, Gregson S, Fearon E, Hensen B, Hallett TB, Hargreaves JRet al., 2019, HIV prevention cascades: a unifying framework to replicate the successes of treatment cascades, LANCET HIV, Vol: 6, Pages: E60-E66, ISSN: 2352-3018

JOURNAL ARTICLE

Anderson S-J, Garnett GP, Enstone J, Hallett TBet al., 2018, The importance of local epidemic conditions in monitoring progress towards HIV epidemic control in Kenya: a modelling study, JOURNAL OF THE INTERNATIONAL AIDS SOCIETY, Vol: 21, ISSN: 1758-2652

JOURNAL ARTICLE

Ghys PD, Williams BG, Over M, Hallett TB, Godfrey-Faussett Pet al., 2018, Epidemiological metrics and benchmarks for a transition in the HIV epidemic, PLOS MEDICINE, Vol: 15, ISSN: 1549-1676

JOURNAL ARTICLE

Fu H, Lin H-H, Hallett TB, Arinaminpathy Net al., 2018, Modelling the effect of discontinuing universal Bacillus Calmette-Guerin vaccination in an intermediate tuberculosis burden setting, VACCINE, Vol: 36, Pages: 5902-5909, ISSN: 0264-410X

JOURNAL ARTICLE

McGillen JB, Stover J, Klein DJ, Xaba S, Ncube G, Mhangara M, Chipendo GN, Taramusi I, Beacroft L, Hallett TB, Odawo P, Manzou R, Korenromp ELet al., 2018, The emerging health impact of voluntary medical male circumcision in Zimbabwe: An evaluation using three epidemiological models, PLOS ONE, Vol: 13, ISSN: 1932-6203

JOURNAL ARTICLE

Phillips A, Cambiano V, Bansi-Matharu L, Nakagawa F, Wilson D, Jani I, Apollo T, Sculpher M, Hallett T, Kerr C, van Oosterhout J, Eaton J, Estill J, Williams B, Doi N, Cowan F, Keiser O, Ford D, Hatzold K, Barnabas R, Ayles H, Meyer-Rath G, Nelson L, Johnson C, Baggaley R, Fakoya A, Jahn A, Revill Pet al., 2018, Cost-of-testing-per-new-HIV-diagnosis as a metric for monitoring cost-effectiveness of testing programmes in low income settings in Southern Africa: health economic modelling analysis, Publisher: JOHN WILEY & SONS LTD, Pages: 27-28, ISSN: 1758-2652

CONFERENCE PAPER

Olney JJ, Eaton JW, Braitstein P, Hogan JW, Hallett TBet al., 2018, Optimal timing of HIV home-based counselling and testing rounds in Western Kenya, JOURNAL OF THE INTERNATIONAL AIDS SOCIETY, Vol: 21, ISSN: 1758-2652

JOURNAL ARTICLE

Heffernan A, Hallett T, Thursz M, Cooke G, Nayagam Set al., 2018, Global scale-up of hepatitis C interventions will reduce burden but not eliminate the disease, 16th International Symposium on Viral Hepatitis and Liver Diseases (ISVHLD), Publisher: WILEY, Pages: 26-26, ISSN: 1352-0504

CONFERENCE PAPER

Meyer-Rath G, McGillen JB, Cuadros DF, Hallett TB, Bhatt S, Wabiri N, Tanser F, Rehle Tet al., 2018, Targeting the right interventions to the right people and places: the role of geospatial analysis in HIV program planning, AIDS, Vol: 32, Pages: 957-963, ISSN: 0269-9370

JOURNAL ARTICLE

Hecht R, Hiebert L, Spearman WC, Sonderup M, Guthrie T, Hallett TB, Nayagam S, Razavi H, Soe-Lin S, Vilakazi-Nhlapo K, Pillay Y, Resch Set al., 2018, The investment case for hepatitis B and C in South Africa: adaptation and innovation in policy analysis for disease program scale-up, HEALTH POLICY AND PLANNING, Vol: 33, Pages: 528-538, ISSN: 0268-1080

JOURNAL ARTICLE

Smit M, Olney J, Ford NP, Vitoria M, Gregson S, Vassall A, Hallett TBet al., 2018, The growing burden of noncommunicable disease among persons living with HIV in Zimbabwe, AIDS, Vol: 32, Pages: 773-782, ISSN: 0269-9370

JOURNAL ARTICLE

Anderson S-J, Ghys PD, Ombam R, Hallett TBet al., 2018, Frontloading HIV financing maximizes the achievable impact of HIV prevention, JOURNAL OF THE INTERNATIONAL AIDS SOCIETY, Vol: 21, ISSN: 1758-2652

JOURNAL ARTICLE

Smit M, van Zoest RA, Nichols BE, Vaartjes I, Smit C, van der Valk M, van Sighem A, Wit FW, Hallett TB, Reiss Pet al., 2018, Cardiovascular Disease Prevention Policy in Human Immunodeficiency Virus: Recommendations From a Modeling Study, CLINICAL INFECTIOUS DISEASES, Vol: 66, Pages: 743-750, ISSN: 1058-4838

JOURNAL ARTICLE

Phillips AN, Cambiano V, Nakagawa F, Revill P, Jordan MR, Hallett TB, Doherty M, De Luca A, Lundgren JD, Mhangara M, Apollo T, Mellors J, Nichols B, Parikh U, Pillay D, de Wit TR, Sigaloff K, Havlir D, Kuritzkes DR, Pozniak A, van de Vijver D, Vitoria M, Wainberg MA, Raizes E, Bertagnolio Set al., 2018, Cost-effectiveness of public-health policy options in the presence of pretreatment NNRTI drug resistance in sub-Saharan Africa: a modelling study, LANCET HIV, Vol: 5, Pages: E146-E154, ISSN: 2352-3018

JOURNAL ARTICLE

Smith MK, Jewell BL, Hallett TB, Cohen MSet al., 2018, Treatment of HIV for the Prevention of Transmission in Discordant Couples and at the Population Level, HIV VACCINES AND CURE: THE PATH TOWARDS FINDING AN EFFECTIVE CURE AND VACCINE, Vol: 1075, Pages: 125-162, ISSN: 0065-2598

JOURNAL ARTICLE

McRobie E, Matovu F, Nanyiti A, Nonvignon J, Abankwah DNY, Case KK, Hallett TB, Hanefeld J, Conteh Let al., 2018, National responses to global health targets: exploring policy transfer in the context of the UNAIDS '90-90-90' treatment targets in Ghana and Uganda, HEALTH POLICY AND PLANNING, Vol: 33, Pages: 17-33, ISSN: 0268-1080

JOURNAL ARTICLE

Woods B, Rothery C, Anderson S-J, Eaton JW, Revill P, Hallett TB, Claxton Ket al., 2018, Appraising the value of evidence generation activities: an HIV modelling study., BMJ Glob Health, Vol: 3, ISSN: 2059-7908

Introduction: The generation of robust evidence has been emphasised as a priority for global health. Evidence generation spans a wide range of activities including clinical trials, surveillance programmes and health system performance measurement. As resources for healthcare and research are limited, the desirability of research expenditure should be assessed on the same basis as other healthcare resources, that is, the health gains from research must be expected to exceed the health opportunity costs imposed as funds are diverted to research rather than service provision. Methods: We developed a transmission and costing model to examine the impact of generating additional evidence to reduce uncertainties on the evolution of a generalised HIV epidemic in Zambia. Results: We demonstrate three important points. First, we can quantify the value of additional evidence in terms of the health gain it is expected to generate. Second, we can quantify the health opportunity cost imposed by research expenditure. Third, the value of evidence generation depends on the budgetary policies in place for managing HIV resources under uncertainty. Generating evidence to reduce uncertainty is particularly valuable when decision makers are required to strictly adhere to expenditure plans and when transfers of funds across geographies/programmes are restricted. Conclusion: Better evidence can lead to health improvements in the same way as direct delivery of healthcare. Quantitative appraisals of evidence generation activities are important and should reflect the impact of improved evidence on population health, evidence generation costs and budgetary policies in place.

JOURNAL ARTICLE

Anderson S-J, Ghys PD, Ombam R, Hallett TBet al., 2017, HIV prevention where it is needed most: comparison of strategies for the geographical allocation of interventions, JOURNAL OF THE INTERNATIONAL AIDS SOCIETY, Vol: 20, ISSN: 1758-2652

JOURNAL ARTICLE

McGillen JB, Sharp A, Honermann B, Millett G, Collins C, Hallett TBet al., 2017, Consequences of a changing US strategy in the global HIV investment landscape, AIDS, Vol: 31, Pages: F19-F23, ISSN: 0269-9370

JOURNAL ARTICLE

Nayagam S, Sicuri E, Lemoine M, Easterbrook P, Conteh L, Hallett TB, Thursz Met al., 2017, Economic evaluations of HBV testing and treatment strategies and applicability to low and middle-income countries, BMC INFECTIOUS DISEASES, Vol: 17, Pages: 107-116, ISSN: 1471-2334

JOURNAL ARTICLE

Smit M, Cassidy R, Cozzi-Lepri A, Quiros-Roldan E, Girardi E, Mammone A, Antinori A, Saracino A, Bai F, Rusconi S, Magnani G, Castelli F, Hsue P, Monforte AD, Hallett TBet al., 2017, Projections of non-communicable disease and health care costs among HIV-positive persons in Italy and the USA: A modelling study, PLOS ONE, Vol: 12, ISSN: 1932-6203

JOURNAL ARTICLE

Gregson S, Mugurungi O, Eaton J, Takaruza A, Rhead R, Maswera R, Mutsvangwa J, Mayini J, Skovdal M, Schaefer R, Hallett T, Sherr L, Munyati S, Mason P, Campbell C, Garnett GP, Nyamukapa CAet al., 2017, Documenting and explaining the HIV decline in east Zimbabwe: the Manicaland General Population Cohort, BMJ OPEN, Vol: 7, ISSN: 2044-6055

JOURNAL ARTICLE

McGillen J, Sharp A, Honermann B, Millett G, Collins C, Hallett Tet al., 2017, How changes in United States funding policies could impact the HIV epidemic in sub-Saharan Africa, Publisher: INT AIDS SOCIETY, Pages: 64-65, ISSN: 1758-2652

CONFERENCE PAPER

Mangal TD, 2017, Joint estimation of CD4(+) cell progression and survival in untreated individuals with HIV-1 infection, AIDS, Vol: 31, Pages: 1073-1082, ISSN: 0269-9370

JOURNAL ARTICLE

Birger RB, Thuy L, Kouyos RD, Grenfell BT, Hallett TBet al., 2017, The impact of HCV therapy in a high HIV-HCV prevalence population: A modeling study on people who inject drugs in Ho Chi Minh City, Vietnam, PLOS ONE, Vol: 12, ISSN: 1932-6203

JOURNAL ARTICLE

Cremin I, McKinnon L, Kimani J, Cherutich P, Gakii G, Muriuki F, Kripke K, Hecht R, Kiragu M, Smith J, Hinsley W, Gelmon L, Hallett TBet al., 2017, PrEP for key populations in combination HIV prevention in Nairobi: a mathematical modelling study, LANCET HIV, Vol: 4, Pages: E214-E222, ISSN: 2352-3018

JOURNAL ARTICLE

Alsallaq RA, Buttolph J, Cleland CM, Hallett T, Inwani I, Agot K, Kurth AEet al., 2017, The potential impact and cost of focusing HIV prevention on young women and men: A modeling analysis in western Kenya, PLOS ONE, Vol: 12, ISSN: 1932-6203

JOURNAL ARTICLE

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