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

212 results found

Odhiambo J, Onyango M, Stover J, Anderson S-J, Klein DJ, Hallett TB, Akullian A, Bershteyn Aet al., 2016, Evaluating the Impact of the Voluntary Medical Male Circumcision (VMMC) Program in Kenya, Conference on HIV Research for Prevention (HIV R4P), Publisher: MARY ANN LIEBERT, INC, Pages: 105-105, ISSN: 0889-2229

Conference paper

Garnett GP, Krishnaratne S, Rush SH, Hallett TB, Hargreaves JRet al., 2016, The Cost-effectiveness, Affordability and Impact of HIV Prevention: Concepts and Reviews, Conference on HIV Research for Prevention (HIV R4P), Publisher: MARY ANN LIEBERT, INC, Pages: 299-299, ISSN: 0889-2229

Conference paper

Bórquez A, Cori A, Pufall EL, Kasule J, Slaymaker E, Price A, Elmes J, Zaba B, Crampin AC, Kagaayi J, Lutalo T, Urassa M, Gregson S, Hallett TBet al., 2016, The Incidence Patterns Model to Estimate the Distribution of New HIV Infections in Sub-Saharan Africa: Development and Validation of a Mathematical Model., PLOS Medicine, Vol: 13, ISSN: 1549-1277

BACKGROUND: Programmatic planning in HIV requires estimates of the distribution of new HIV infections according to identifiable characteristics of individuals. In sub-Saharan Africa, robust routine data sources and historical epidemiological observations are available to inform and validate such estimates. METHODS AND FINDINGS: We developed a predictive model, the Incidence Patterns Model (IPM), representing populations according to factors that have been demonstrated to be strongly associated with HIV acquisition risk: gender, marital/sexual activity status, geographic location, "key populations" based on risk behaviours (sex work, injecting drug use, and male-to-male sex), HIV and ART status within married or cohabiting unions, and circumcision status. The IPM estimates the distribution of new infections acquired by group based on these factors within a Bayesian framework accounting for regional prior information on demographic and epidemiological characteristics from trials or observational studies. We validated and trained the model against direct observations of HIV incidence by group in seven rounds of cohort data from four studies ("sites") conducted in Manicaland, Zimbabwe; Rakai, Uganda; Karonga, Malawi; and Kisesa, Tanzania. The IPM performed well, with the projections' credible intervals for the proportion of new infections per group overlapping the data's confidence intervals for all groups in all rounds of data. In terms of geographical distribution, the projections' credible intervals overlapped the confidence intervals for four out of seven rounds, which were used as proxies for administrative divisions in a country. We assessed model performance after internal training (within one site) and external training (between sites) by comparing mean posterior log-likelihoods and used the best model to estimate the distribution of HIV incidence in six countries (Gabon, Kenya, Malawi, Rwanda, Swaziland, and Zambia) in the region. We subsequ

Journal article

Nayagam S, Thursz M, Sicuri E, Conteh L, Wiktor S, Low-Beer D, Hallett TBet al., 2016, Requirements for global elimination of hepatitis B: a modelling study., Lancet Infectious Diseases, Vol: 16, Pages: 1399-1408, ISSN: 1473-3099

BackgroundDespite the existence of effective prevention and treatment interventions, hepatitis B virus (HBV) infection continues to cause nearly 1 million deaths each year. WHO aspires to global control and elimination of HBV infection. We aimed to evaluate the potential impact of public health interventions against HBV, propose targets for reducing incidence and mortality, and identify the key developments required to achieve them.MethodsWe developed a simulation model of the global HBV epidemic, incorporating data on the natural history of HBV, prevalence, mortality, vaccine coverage, treatment dynamics, and demographics. We estimate the impact of current interventions and scaling up of existing interventions for prevention of infection and introducing wide-scale population screening and treatment interventions on the worldwide epidemic.FindingsVaccination of infants and neonates is already driving a large decrease in new infections; vaccination has already prevented 210 million new chronic infections by 2015 and will have averted 1·1 million deaths by 2030. However, without scale-up of existing interventions, our model showed that there will be a cumulative 63 million new cases of chronic infection and 17 million HBV-related deaths between 2015 and 2030 because of ongoing transmission in some regions and poor access to treatment for people already infected. A target of a 90% reduction in new chronic infections and 65% reduction in mortality could be achieved by scaling up the coverage of infant vaccination (to 90% of infants), birth-dose vaccination (to 80% of neonates), use of peripartum antivirals (to 80% of hepatitis B e antigen-positive mothers), and population-wide testing and treatment (to 80% of eligible people). These interventions would avert 7·3 million deaths between 2015 and 2030, including 1·5 million cases of cancer deaths. An elimination threshold for incidence of new chronic infections would be reached by 2090 worldwide. The a

Journal article

McGillen JB, Anderson SJ, Dybul MR, Hallett TBet al., 2016, Optimum resource allocation to reduce HIV incidence across sub-Saharan Africa: a mathematical modelling study, Lancet HIV, Vol: 3, Pages: e441-e448, ISSN: 2352-3018

BACKGROUND: Advances in HIV prevention methods offer promise to accelerate declines in incidence, but how these methods can be deployed to have the best effect on the heterogeneous landscape and drivers of the pandemic remains unclear. We postulated that use of epidemic heterogeneity to inform the allocation of resources for combination HIV prevention could enhance the impact of HIV funding across sub-Saharan Africa. METHODS: We developed a compartmental mathematical model of HIV transmission and disease progression by risk group to subnational resolution in 18 countries, capturing 80% of the adult HIV burden in sub-Saharan Africa. Adults aged 15-49 years were grouped by risk of HIV acquisition and transmission, and those older than 50 years were assumed to have negligible risk. For each top-level administrative division, we calibrated the model to historical data for HIV prevalence, sexual behaviours, treatment scale-up, and demographics. We then evaluated four strategies for allocation of prevention funding over a 15 year period from 2016 to 2030, which exploited epidemic differences between subnational regions to varying degrees. FINDINGS: For a $US20 billion representative expenditure over the 15 year period, scale-up of prevention along present funding channels could avert 5·3 million infections relative to no scale-up. Prioritisation of key populations could avert 3·7 million more infections than present funding channels, and additional prioritisation by within-country geography could avert 400 000 more infections. Removal of national constraints could avert a further 600 000 infections. Risk prioritisation has greater marginal impact than geographical prioritisation across multiple expenditure levels. However, targeting by both risk and geography is best for total impact and could achieve gains of up to three times more than present channels. A shift from the present pattern to the optimum pattern would rebalance resources towards more cost-effe

Journal article

Nayagam S, Conteh L, Sicuri E, Shimakawa Y, Tamba S, Suso P, Njie R, Njai H, Lemoine M, Hallett TB, Thursz Met al., 2016, Cost-effectiveness of community-based screening and treatment for chronic hepatitis B in The Gambia: an economic modelling analysis, Lancet Global Health, Vol: 4, Pages: e568-e578, ISSN: 2214-109X

Background: Despite the high burden of hepatitis B virus (HBV)infection in sub-Saharan Africa (SSA), a lack of access to widespreadscreening or treatment leads to most people remaining undiagnosed untillater stages of disease when prognosis is poor and treatment options arelimited. We evaluated the cost-effectiveness of community-based screeningand early treatment with antiviral therapy for HBV in The Gambia.Methods: An economic evaluation comparing adult community-based screeningusing a Hepatitis B surface antigen (HBsAg) rapid test and subsequent HBVantiviral therapy to a status quo scenario, where no treatment isavailable, was performed by combining a decision tree with a Markov statetransition model. This was parameterised with primary screening and costdata from the PROLIFICA study. A health provider perspective was takenand costs and health outcomes were discounted at 3% per annum.Findings: In The Gambia, where the HBsAg prevalence is 8.8% among thoseaged over 30 years old, adult screening and treatment for HBV, has anIncremental Cost-Effectiveness Ratio (ICER) of $540 per DisabilityAdjusted Life Year (DALY) averted, $645 per Life Year (LY) saved and $511per Quality Adjusted Life Year (QALY) gained, compared to status quo.These ICERs are in line with willingness-to-pay levels of one times thecountry's Gross Domestic Product (GDP) per capita ($487) per DALYaverted, whilst remaining robust, over a wide range of epidemiologicaland cost parameters.Interpretation: Adult community-based screening and treatment for HBV inthe Gambia is likely to be a cost-effective intervention with an ICERthat is comparable with those of HIV screening and treatmentinterventions in SSA. Even higher cost-effectiveness, may be achievablewith targeted facility-based screening, price reductions of drug and diagnostics and integration of HBV screening with other public healthinterventions.

Journal article

Dimitrov DT, Boily MC, Hallett TB, Albert J, Boucher C, Mellors JW, Pillay D, van de Vijver DAet al., 2016, How Much Do We Know about Drug Resistance Due to PrEP Use? Analysis of Experts’ Opinion and Its Influence on the Projected Public Health Impact, PLOS One, Vol: 11, ISSN: 1932-6203

BACKGROUND: Randomized controlled trials reported that pre-exposure prophylaxis (PrEP) with tenofovir and emtricitabine rarely selects for drug resistance. However, drug resistance due to PrEP is not completely understood. In daily practice, PrEP will not be used under the well-controlled conditions available in the trials, suggesting that widespread use of PrEP can result in increased drug resistance. METHODS: We surveyed expert virologists with questions about biological assumptions regarding drug resistance due to PrEP use. The influence of these assumptions on the prevalence of drug resistance and the fraction of HIV transmitted resistance was studied with a mathematical model. For comparability, 50% PrEP-coverage of and 90% per-act efficacy of PrEP in preventing HIV acquisition are assumed in all simulations. RESULTS: Virologists disagreed on the following: the time until resistance emergence (range: 20-180 days) in infected PrEP users with breakthrough HIV infections; the efficacy of PrEP against drug-resistant HIV (25%-90%); and the likelihood of resistance acquisition upon transmission (10%-75%). These differences translate into projections of 0.6%- 1% and 3.5%-6% infected individuals with detectable resistance 10 years after introducing PrEP, assuming 100% and 50% adherence, respectively. The rate of resistance emergence following breakthrough HIV infection and the rate of resistance reversion after PrEP use is discontinued, were the factors identified as most influential on the expected resistance associated with PrEP. Importantly, 17-23% infected individuals could virologically fail treatment as a result of past PrEP use or transmitted resistance to PrEP with moderate adherence. CONCLUSIONS: There is no broad consensus on quantification of key biological processes that underpin the emergence of PrEP-associated drug resistance. Despite this, the contribution of PrEP use to the prevalence of the detectable drug resistance is expected to be small. However, i

Journal article

Hargreaves JR, Delany-Moretlwe S, Hallett TB, Johnson S, Kapiga S, Bhattacharjee P, Dallabetta G, Garnett GPet al., 2016, The HIV prevention cascade: integrating theories of epidemiological, behavioural, and social science into programme design and monitoring, The Lancet HIV, Vol: 3, Pages: E318-E322, ISSN: 2352-3018

Theories of epidemiology, health behaviour, and social science have changed the understanding of HIV prevention in the past three decades. The HIV prevention cascade is emerging as a new approach to guide the design and monitoring of HIV prevention programmes in a way that integrates these multiple perspectives. This approach recognises that translating the efficacy of direct mechanisms that mediate HIV prevention (including prevention products, procedures, and risk-reduction behaviours) into population-level effects requires interventions that increase coverage. An HIV prevention cascade approach suggests that high coverage can be achieved by targeting three key components: demand-side interventions that improve risk perception and awareness and acceptability of prevention approaches; supply-side interventions that make prevention products and procedures more accessible and available; and adherence interventions that support ongoing adoption of prevention behaviours, including those that do and do not involve prevention products. Programmes need to develop delivery platforms that ensure these interventions reach target populations, to shape the policy environment so that it facilitates implementation at scale with high quality and intensity, and to monitor the programme with indicators along the cascade.

Journal article

Garnett GP, Hallett TB, Takaruza A, Hargreaves J, Rhead R, Warren M, Nyamukapa C, Gregson Set al., 2016, Providing a conceptual framework for HIV prevention cascades and assessing feasibility of empirical measurement with data from east Zimbabwe: a case study, Lancet HIV, Vol: 3, Pages: E297-E306, ISSN: 2352-3018

BackgroundThe HIV treatment cascade illustrates the steps required for successful treatment and is a powerful advocacy and monitoring tool. Similar cascades for people susceptible to infection could improve HIV prevention programming. We aim to show the feasibility of using cascade models to monitor prevention programmes.MethodsConceptual prevention cascades are described taking intervention-centric and client-centric perspectives to look at supply, demand, and efficacy of interventions. Data from two rounds of a population-based study in east Zimbabwe are used to derive the values of steps for cascades for voluntary medical male circumcision (VMMC) and for partner reduction or condom use driven by HIV testing and counselling (HTC).FindingsIn 2009 to 2011 the availability of circumcision services was negligible, but by 2012 to 2013 about a third of the population had access. However, where it was available only 12% of eligible men sought to be circumcised leading to an increase in circumcision prevalence from 3·1% to 6·9%. Of uninfected men, 85·3% did not perceive themselves to be at risk of acquiring HIV. The proportions of men and women tested for HIV increased from 27·5% to 56·6% and from 61·1% to 79·6%, respectively, with 30·4% of men tested self-reporting reduced sexual partner numbers and 12·8% reporting increased condom use.InterpretationPrevention cascades can be populated to inform HIV prevention programmes. In eastern Zimbabwe programmes need to provide greater access to circumcision services and the design and implementation of associated demand creation activities. Whereas, HTC services need to consider how to increase reductions in partner numbers or increased condom use or should not be considered as contributing to prevention services for the HIV-negative adults.

Journal article

Phillips AN, Cambiano V, Revill P, Nakagawa F, Lundgren JD, Bansi-Matharu L, Mabugu T, Sculpher M, Garnett G, Staprans S, Becker S, Murungu J, Lewin SR, Deeks SG, Hallett TBet al., 2016, Identifying Key Drivers of the Impact of an HIV Cure Intervention in Sub-Saharan Africa, Journal of Infectious Diseases, Vol: 214, Pages: 73-79, ISSN: 1537-6613

BACKGROUND: It is unknown what properties would be required to make an intervention in low income countries that can eradicate or control human immunodeficiency virus (HIV) without antiretroviral therapy (ART) cost-effective. METHODS: We used a model of HIV and ART to investigate the effect of introducing an ART-free viral suppression intervention in 2022 using Zimbabwe as an example country. We assumed that the intervention (cost: $500) would be accessible for 90% of the population, be given to those receiving effective ART, have sufficient efficacy to allow ART interruption in 95%, with a rate of viral rebound of 5% per year in the first 3 months, and a 50% decline in rate with each successive year. RESULTS: An ART-free viral suppression intervention with these properties would result in >0.53 million disability-adjusted-life-years averted over 2022-2042, with a reduction in HIV program costs of $300 million (8.7% saving). An intervention of this efficacy costing anything up to $1400 is likely to be cost-effective in this setting. CONCLUSIONS: Interventions aimed at curing HIV infection have the potential to improve overall disease burden and to reduce costs. Given the effectiveness and cost of ART, such interventions would have to be inexpensive and highly effective.

Journal article

Smith JA, Anderson SJ, Harris KL, McGillen JB, Lee E, Garnett GP, Hallett TBet al., 2016, Maximising HIV prevention - balancing the opportunities of today with the promises of tomorrow: a modelling study, The Lancet HIV, Vol: 3, Pages: e289-e296, ISSN: 2352-3018

Background: Many ways of preventing HIV infection have been proposed and more are being developed. We sought to construct a strategic approach to HIV prevention that would use limited resources to achieve the greatest possible prevention impact through the use of interventions available today and in the coming years.Methods: We developed a mathematical model of the HIV epidemic in South Africa and formed assumptions about the costs and effects of a range of interventions, encompassing the further scale-up of existing interventions (promoting condom use, male circumcision, outreach testing and early ART initiation for all, and oral PrEP), the introduction of new interventions in the medium-term (offering intravaginal rings (IVR), long-acting antiretrovirals (LA-ARVS)) and long-term (vaccine, broadly neutralising antibodies (bNAbs)). We examined how available resources could be allocated across these interventions to achieve maximal impact, and assessed how this would be affected by the failure of the interventions to be developed or scaled up.Findings: If all the above-listed interventions are available, the optimal mix of interventions would place great emphasis on: (i) scale-up of male circumcision and outreach testing and ART initiation, as these are available immediately and are assumed to be low cost and/or highly efficacious; (ii) IVR targeted to sex workers; and (iii) vaccines, as these can achieve a high impact if scaled-up even if imperfectly efficacious. It would rely less on longer-term developments, such as LA-ARVS and bNAbs, unless the costs of these reduced. However, if it were not possible to scale up existing interventions to the extent assumed, greater emphasis would be placed on oral PrEP, IVR and LA-ARVs. The long-term impact on the epidemic is most affected by scale-up of existing interventions and the successful development of a vaccine.Interpretation: With current information, a strategic approach in which limited resources are used to maximise

Journal article

Hallett TB, Anderson S-J, Asante CA, Bartlett N, Bendaud V, Bhatt S, Burgert CR, Cuadros DF, Dzangare J, Fecht D, Gething PW, Ghys PD, Guwani JM, Heard NJ, Kalipeni E, Kandala N-B, Kim AA, Kwao ID, Larmarange J, Manda SOM, Moise IK, Montana LS, Mwai DN, Mwalili S, Shortridge A, Tanser F, Wanyeki I, Zulu Let al., 2016, Evaluation of geospatial methods to generate subnational HIV prevalence estimates for local level planning, AIDS, Vol: 30, Pages: 1467-1474, ISSN: 0269-9370

Objective: There is evidence of substantial subnational variation in the HIV epidemic. However, robust spatial HIV data are often only available at high levels of geographic aggregation and not at the finer resolution needed for decision making. Therefore, spatial analysis methods that leverage available data to provide local estimates of HIV prevalence may be useful. Such methods exist but have not been formally compared when applied to HIV.Design/methods: Six candidate methods – including those used by the Joint United Nations Programme on HIV/AIDS to generate maps and a Bayesian geostatistical approach applied to other diseases – were used to generate maps and subnational estimates of HIV prevalence across three countries using cluster level data from household surveys. Two approaches were used to assess the accuracy of predictions: internal validation, whereby a proportion of input data is held back (test dataset) to challenge predictions; and comparison with location-specific data from household surveys in earlier years.Results: Each of the methods can generate usefully accurate predictions of prevalence at unsampled locations, with the magnitude of the error in predictions similar across approaches. However, the Bayesian geostatistical approach consistently gave marginally the strongest statistical performance across countries and validation procedures.Conclusions: Available methods may be able to furnish estimates of HIV prevalence at finer spatial scales than the data currently allow. The subnational variation revealed can be integrated into planning to ensure responsiveness to the spatial features of the epidemic. The Bayesian geostatistical approach is a promising strategy for integrating HIV data to generate robust local estimates.

Journal article

Cooke GS, Hallett T, 2016, HCV and HIV: shared challenges, shared solutions., Lancet Infectious Diseases, ISSN: 1473-3099

Journal article

Cremin I, Morales F, Jewell BL, O'Reilly KR, Hallett TBet al., 2016, Seasonal PrEP for partners of migrant miners in southern Mozambique: a highly focused PrEP intervention (vol 18, 19946, 2015), JOURNAL OF THE INTERNATIONAL AIDS SOCIETY, Vol: 19

Journal article

Smit M, Hallett T, 2016, Respiratory co-morbidities in people with HIV, Lancet Infectious Diseases, Vol: 16, Pages: 152-152, ISSN: 1473-3099

Journal article

Nayagam S, Chan P, Zhao K, Sicuri E, Wang X, Jia J, Wei L, Walsh N, Rodewald LE, Zhang G, Ailing W, Lixia D, Chang J, Hou W, Qiu Y, Sui B, Xiao Y, Zhuang H, Thursz M, Scano F, Low-Beer D, Schwartlaender B, Wang Y, Hallett Tet al., 2016, INVESTMENT CASE FOR A COMPREHENSIVE PACKAGE OF INTERVENTIONS AGAINST HEPATITIS B IN CHINA, EASL International Liver Congress, Publisher: ELSEVIER SCIENCE BV, Pages: S469-S469, ISSN: 0168-8278

Conference paper

Phillips A, Shroufi A, Vojnov L, Cohn J, Roberts T, Ellman T, Bonner K, Rousseau C, Garnett G, Cambiano V, Nakagawa F, Ford D, Bansi-Matharu L, Miners A, Lundgren JD, Eaton JW, Parkes-Ratanshi R, Katz Z, Maman D, Ford N, Vitoria M, Doherty M, Dowdy D, Nichols B, Murtagh M, Wareham M, Palamountain KM, Musanhu CC, Stevens W, Katzenstein D, Ciaranello A, Barnabas R, Braithwaite RS, Bendavid E, Nathoo KJ, van de Vijver D, Wilson DP, Holmes C, Bershteyn A, Walker S, Raizes E, Jani I, Nelson LJ, Peeling R, Terris-Prestholt F, Murungu J, Mutasa-Apollo T, Hallett TB, Revill Pet al., 2015, Sustainable HIV treatment in Africa through viral-load-informed differentiated care, Nature, Vol: 528, Pages: S68-S76, ISSN: 1476-4687

Journal article

Eaton JW, Bacaer N, Bershteyn A, Cambiano V, Cori A, Dorrington RE, Fraser C, Gopalappa C, Hontelez JAC, Johnson LF, Klein DJ, Phillips AN, Pretorius C, Stover J, Rehle TM, Hallett TBet al., 2015, Assessment of epidemic projections using recent HIV survey data in South Africa: a validation analysis of ten mathematical models of HIV epidemiology in the antiretroviral therapy era, Lancet Global Health, Vol: 3, Pages: e598-e608, ISSN: 2214-109X

BackgroundMathematical models are widely used to simulate the effects of interventions to control HIV and to project future epidemiological trends and resource needs. We aimed to validate past model projections against data from a large household survey done in South Africa in 2012.MethodsWe compared ten model projections of HIV prevalence, HIV incidence, and antiretroviral therapy (ART) coverage for South Africa with estimates from national household survey data from 2012. Model projections for 2012 were made before the publication of the 2012 household survey. We compared adult (age 15–49 years) HIV prevalence in 2012, the change in prevalence between 2008 and 2012, and prevalence, incidence, and ART coverage by sex and by age groups between model projections and the 2012 household survey.FindingsAll models projected lower prevalence estimates for 2012 than the survey estimate (18·8%), with eight models' central projections being below the survey 95% CI (17·5–20·3). Eight models projected that HIV prevalence would remain unchanged (n=5) or decline (n=3) between 2008 and 2012, whereas prevalence estimates from the household surveys increased from 16·9% in 2008 to 18·8% in 2012 (difference 1·9, 95% CI −0·1 to 3·9). Model projections accurately predicted the 1·6 percentage point prevalence decline (95% CI −0·3 to 3·5) in young adults aged 15–24 years, and the 2·2 percentage point (0·5 to 3·9) increase in those aged 50 years and older. Models accurately represented the number of adults on ART in 2012; six of ten models were within the survey 95% CI of 1·54–2·12 million. However, the differential ART coverage between women and men was not fully captured; all model projections of the sex ratio of women to men on ART were lower than the survey estimate of 2·22 (95% CI 1·73–2·71).InterpretationProjec

Journal article

Rehle T, Johnson L, Hallett T, Mahy M, Kim A, Odido H, Onoya D, Jooste S, Shisana O, Puren A, Parekh B, Stover Jet al., 2015, A Comparison of South African National HIV Incidence Estimates: A Critical Appraisal of Different Methods, PLOS One, Vol: 10, ISSN: 1932-6203

BackgroundThe interpretation of HIV prevalence trends is increasingly difficult as antiretroviral treatment programs expand. Reliable HIV incidence estimates are critical to monitoring transmission trends and guiding an effective national response to the epidemic.Methods and FindingsWe used a range of methods to estimate HIV incidence in South Africa: (i) an incidence testing algorithm applying the Limiting-Antigen Avidity Assay (LAg-Avidity EIA) in combination with antiretroviral drug and HIV viral load testing; (ii) a modelling technique based on the synthetic cohort principle; and (iii) two dynamic mathematical models, the EPP/Spectrum model package and the Thembisa model. Overall, the different incidence estimation methods were in broad agreement on HIV incidence estimates among persons aged 15-49 years in 2012. The assay-based method produced slightly higher estimates of incidence, 1.72% (95% CI 1.38 – 2.06), compared with the mathematical models, 1.47% (95% CI 1.23 – 1.72) in Thembisa and 1.52% (95% CI 1.43 – 1.62) in EPP/Spectrum, and slightly lower estimates of incidence compared to the synthetic cohort, 1.9% (95% CI 0.8 – 3.1) over the period from 2008 to 2012. Among youth aged 15-24 years, a declining trend in HIV incidence was estimated by all three mathematical estimation methods.ConclusionsThe multi-method comparison showed similar levels and trends in HIV incidence and validated the estimates provided by the assay-based incidence testing algorithm. Our results confirm that South Africa is the country with the largest number of new HIV infections in the world, with about 1 000 new infections occurring each day among adults aged 15-49 years in 2012.

Journal article

Cremin I, Morales F, Jewell BL, O'Reilly KR, Hallett TBet al., 2015, Seasonal PrEP for partners of migrant miners in southern Mozambique: a highly focused PrEP intervention, Journal of the International AIDS Society, Vol: 18, ISSN: 1758-2652

Introduction: To be used most effectively, pre-exposure prophylaxis (PrEP) should be prioritized to those at high risk of acquisition and would ideally be aligned with time periods of increased exposure. Identifying such time periods is not always straightforward, however. Gaza Province in southern Mozambique is characterized by high levels of HIV transmission and circular labour migration to mines in South Africa. A strong seasonal pattern in births is observable, reflecting an increase in conception in December. Given the potential for increased HIV transmission between miners returning in December and their partners in Gaza Province, PrEP use by the latter would be a useful means of HIV prevention, especially for couples who wish to conceive.Methods: A mathematical model was used to represent population-level adult heterosexual HIV transmission in Gaza Province. Increased HIV acquisition among partners of miners in December, coinciding with the miners’ return from South Africa, is represented. In addition to a PrEP intervention, the scale-up of treatment and recent scale-up of male circumcision that have occurred in Gaza are represented.Results: Providing time-limited PrEP to the partners of migrant miners, as opposed to providing PrEP all year, would improve the cost per infection averted by 7.5-fold. For the cost per infection averted to be below US$3000, at least 85% of PrEP users would need to be good adherers and PrEP would need to be cheaper than US$115 per person per year. Uncertainty regarding incidence of HIV transmission among partners of miners each year in December has a strong influence on estimates of cost per infection averted.Conclusions: Providing time-limited PrEP to partners of migrant miners in Gaza Province during periods of increased exposure would be a novel strategy for providing PrEP. This strategy would allow for a better prioritized intervention, with the potential to improve the efficiency of a PrEP intervention considerably, as

Journal article

Smit M, Brinkman K, Geerlings S, Smit C, Thyagarajan K, van Sighem A, de Wolf F, Hallett TBet al., 2015, Future challenges for clinical care of an ageing population infected with HIV: a modelling study, Lancet Infectious Diseases, Vol: 15, Pages: 810-818, ISSN: 1473-3099

Background The population infected with HIV is getting older and these people will increasingly develop age-relatednon-communicable diseases (NCDs). We aimed to quantify the scale of the change and the implications for HIV carein the Netherlands in the future.Methods We constructed an individual-based model of the ageing HIV-infected population, which followed patientson HIV treatment as they age, develop NCDs—including cardiovascular disease (hypertension, hypercholesterolaemia,myocardial infarctions, and strokes), diabetes, chronic kidney disease, osteoporosis, and non-AIDS malignancies—and start co-medication for these diseases. The model was parameterised by use of data for 10 278 patients from thenational Dutch ATHENA cohort between 1996 and 2010. We made projections up to 2030.Findings Our model suggests that the median age of HIV-infected patients on combination antiretroviral therapy(ART) will increase from 43·9 years in 2010 to 56·6 in 2030, with the proportion of HIV-infected patients aged50 years or older increasing from 28% in 2010 to 73% in 2030. In 2030, we predict that 84% of HIV-infected patientswill have at least one NCD, up from 29% in 2010, with 28% of HIV-infected patients in 2030 having three or moreNCDs. 54% of HIV-infected patients will be prescribed co-medications in 2030, compared with 13% in 2010, with20% taking three or more co-medications. Most of this change will be driven by increasing prevalence ofcardiovascular disease and associated drugs. Because of contraindications and drug–drug interactions, in 2030, 40%of patients could have complications with the currently recommended fi rst-line HIV regimens.Interpretation The profi le of patients in the Netherlands infected with HIV is changing, with increasing numbers ofolder patients with multiple morbidities. These changes mean that, in the near future, HIV care will increasingly need todraw on a wide range of medical disciplines, in addition to evidence-bas

Journal article

Nayagam S, Thursz M, Wiktor S, Low-Beer D, Hallett Tet al., 2015, WHAT IS REQUIRED FOR CONTROL AND ELIMINATION OF HEPATITIS B GLOBALLY?, 2nd Digestive-Disorders-Federation Conference, Publisher: BMJ PUBLISHING GROUP, Pages: A112-A112, ISSN: 0017-5749

Conference paper

Woodall H, Martin N, Hallett T, Cooke G, Hickman M, Vickerman Pet al., 2015, WHAT IS NEEDED TO CONTROL HEPATITIS C (HCV) IN DIFFERENT EPIDEMIOLOGICAL SETTINGS?, 50th International Liver Congress of the European-Association-for-the-Study-of-the-Liver, Publisher: ELSEVIER SCIENCE BV, Pages: S839-S840, ISSN: 0168-8278

Conference paper

Nayagam S, Thursz M, Wiktor S, Low-Beer D, Hallett Tet al., 2015, WHAT IS REQUIRED FOR CONTROL AND ELIMINATION OF HEPATITIS B GLOBALLY?, 50th International Liver Congress of the European-Association-for-the-Study-of-the-Liver, Publisher: ELSEVIER SCIENCE BV, Pages: S285-S285, ISSN: 0168-8278

Conference paper

Cremin I, Hallett TB, 2015, Estimating the range of potential epidemiological impact of pre-exposure prophylaxis: run-away success or run-away failure?, AIDS, Vol: 29, Pages: 733-738, ISSN: 0269-9370

Journal article

Smith JA, Sharma M, Levin C, Baeten JM, van Rooyen H, Celum C, Hallett TB, Barnabas RVet al., 2015, Cost-effectiveness of community-based strategies to strengthen the continuum of HIV care in rural South Africa: a health economic modelling analysis, Lancet HIV, Vol: 2, Pages: e159-e168, ISSN: 2352-3018

BackgroundHome HIV counselling and testing (HTC) achieves high coverage of testing and linkage to care compared with existing facility-based approaches, particularly among asymptomatic individuals. In a modelling analysis we aimed to assess the effect on population-level health and cost-effectiveness of a community-based package of home HTC in KwaZulu-Natal, South Africa.MethodsWe parameterised an individual-based model with data from home HTC and linkage field studies that achieved high coverage (91%) and linkage to antiretroviral therapy (80%) in rural KwaZulu-Natal, South Africa. Costs were derived from a linked microcosting study. The model simulated 10 000 individuals over 10 years and incremental cost-effectiveness ratios were calculated for the intervention relative to the existing status quo of facility-based testing, with costs discounted at 3% annually.FindingsThe model predicted implementation of home HTC in addition to current practice to decrease HIV-associated morbidity by 10–22% and HIV infections by 9–48% with increasing CD4 cell count thresholds for antiretroviral therapy initiation. Incremental programme costs were US$2·7 million to $4·4 million higher in the intervention scenarios than at baseline, and costs increased with higher CD4 cell count thresholds for antiretroviral therapy initiation; antiretroviral therapy accounted for 48–87% of total costs. Incremental cost-effectiveness ratios per disability-adjusted life-year averted were $1340 at an antiretroviral therapy threshold of CD4 count lower than 200 cells per μL, $1090 at lower than 350 cells per μL, $1150 at lower than 500 cells per μL, and $1360 at universal access to antiretroviral therapy.InterpretationCommunity-based HTC with enhanced linkage to care can result in increased HIV testing coverage and treatment uptake, decreasing the population burden of HIV-associated morbidity and mortality. The incremental cost-effectiveness ratios are less tha

Journal article

Jewell BL, Cremin I, Pickles M, Celum C, Baeten JM, Delany-Moretlwe S, Hallett TBet al., 2015, Estimating the cost-effectiveness of pre-exposure prophylaxis to reduce HIV-1 and HSV-2 incidence in HIV-serodiscordant couples in South Africa, PLOS One, Vol: 10, ISSN: 1932-6203

ObjectiveTo estimate the cost-effectiveness of daily oral tenofovir-based PrEP, with a protective effect against HSV-2 as well as HIV-1, among HIV-1 serodiscordant couples in South Africa.MethodsWe incorporated HSV-2 acquisition, transmission, and interaction with HIV-1 into a microsimulation model of heterosexual HIV-1 serodiscordant couples in South Africa, with use of PrEP for the HIV-1 uninfected partner prior to ART initiation for the HIV-1 1infected partner, and for one year thereafter.ResultsWe estimate the cost per disability-adjusted life-year (DALY) averted for two scenarios, one in which PrEP has no effect on reducing HSV-2 acquisition, and one in which there is a 33% reduction. After a twenty-year intervention, the cost per DALY averted is estimated to be $10,383 and $9,757, respectively – a 6% reduction, given the additional benefit of reduced HSV-2 acquisition. If all couples are discordant for both HIV-1 and HSV-2, the cost per DALY averted falls to $1,445, which shows that the impact is limited by HSV-2 concordance in couples.ConclusionAfter a 20-year PrEP intervention, the cost per DALY averted with a reduction in HSV-2 is estimated to be modestly lower than without any effect, providing an increase of health benefits in addition to HIV-1 prevention at no extra cost. The small degree of the effect is in part due to a high prevalence of HSV-2 infection in HIV-1 serodiscordant couples in South Africa.

Journal article

Nichols BE, Sigaloff KCE, Kityo C, Hamers RL, Baltussen R, Bertagnolio S, Jordan MR, Hallett TB, Boucher CAB, de Wit TFR, van de Vijver DAMCet al., 2014, Increasing the use of second-line therapy is a cost-effective approach to prevent the spread of drug-resistant HIV: a mathematical modelling study, JOURNAL OF THE INTERNATIONAL AIDS SOCIETY, Vol: 17

Journal article

Elmes J, Nhongo K, Ward H, Hallett T, Nyamukapa C, White PJ, Gregson Set al., 2014, The Price of Sex: Condom Use and the Determinants of the Price of Sex Among Female Sex Workers in Eastern Zimbabwe, JOURNAL OF INFECTIOUS DISEASES, Vol: 210, Pages: S569-S578, ISSN: 0022-1899

Journal article

Eaton JW, Hallett TB, 2014, Why the proportion of transmission during early-stage HIV infection does not predict the long-term impact of treatment on HIV incidence, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 111, Pages: 16202-16207, ISSN: 0027-8424

Journal article

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