Publications
290 results found
Borquez A, Silva-Santisteban A, Guanira J, et al., 2015, IMPACT AND COST-EFFECTIVENESS OF HIV PREVENTION INTERVENTIONS AMONG TRANSGENDER WOMEN SEX-WORKERS IN LIMA, PERU USING MATHEMATICAL MODELLING INFORMED BY STAKEHOLDER ANALYSIS AND HEALTH SYSTEM CAPACITY EVALUATION, Publisher: BMJ PUBLISHING GROUP, Pages: A52-A52, ISSN: 1368-4973
Borquez A, Cori A, Pufall E, et al., 2015, ESTIMATING THE DISTRIBUTION OF NEW HIV INFECTIONS BY KEY DETERMINANTS IN GENERALISED EPIDEMICS OF SUB-SAHARAN AFRICA USING A VALIDATED MATHEMATICAL MODEL, Publisher: BMJ PUBLISHING GROUP, Pages: A215-A216, ISSN: 1368-4973
Rehle T, Johnson L, Hallett T, et 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.
Cremin I, Morales F, Jewell BL, et 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
Smit M, Brinkman K, Geerlings S, et 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
Nayagam S, Thursz M, Wiktor S, et 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
Gregson S, Hallett TB, 2015, Population Structure and Public Health Research on HIV Control in Sub-Saharan Africa, Population in the Human Sciences: Concepts, Models, Evidence, ISBN: 9780199688203
The Human Immunodeficiency Virus type 1 (HIV-1) has been a major public health disaster in sub-Saharan Africa since the late 1970s. Early projections of HIV epidemics in Africa and their likely demographic consequences were criticized for failing to account for population age structure. With hindsight, age structure per se had relatively little influence on the size of epidemics. However, other aspects of population structure- particularly heterogeneities in sexual behaviour-have been key determinants in the scale and temporal dynamics of HIV epidemics. This chapter explains how an understanding of the influence of population structure on the dynamics of HIV epidemics is important in understanding observed trends in national epidemics, in evaluating the effectiveness of national control programmes, and in prioritizing intervention efforts.
Nayagam S, Thursz M, Wiktor S, et 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
Woodall H, Martin N, Hallett T, et 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
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
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- Citations: 15
Smith JA, Sharma M, Levin C, et 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
Jewell BL, Cremin I, Pickles M, et 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.
Nichols BE, Sigaloff KCE, Kityo C, et 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
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- Citations: 22
Elmes J, Nhongo K, Ward H, et 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
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- Citations: 36
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
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- Citations: 37
Stover J, Hallett TB, Wu Z, et al., 2014, How Can We Get Close to Zero? The Potential Contribution of Biomedical Prevention and the Investment Framework towards an Effective Response to HIV, PLOS One, Vol: 9, ISSN: 1932-6203
Background: In 2011 an Investment Framework was proposed that described how the scale-up of key HIV interventionscould dramatically reduce new HIV infections and deaths in low and middle income countries by 2015. This frameworkincluded ambitious coverage goals for prevention and treatment services resulting in a reduction of new HIV infections bymore than half. However, it also estimated a leveling in the number of new infections at about 1 million annually after 2015.Methods: We modeled how the response to AIDS can be further expanded by scaling up antiretroviral treatment (ART)within the framework provided by the 2013 WHO treatment guidelines. We further explored the potential contributions ofnew prevention technologies: ‘Test and Treat’, pre-exposure prophylaxis and an HIV vaccine.Findings: Immediate aggressive scale up of existing approaches including the 2013 WHO guidelines could reduce newinfections by 80%. A ‘Test and Treat’ approach could further reduce new infections. This could be further enhanced by afuture highly effective pre-exposure prophylaxis and an HIV vaccine, so that a combination of all four approaches couldreduce new infections to as low as 80,000 per year by 2050 and annual AIDS deaths to 260,000.Interpretation: In a set of ambitious scenarios, we find that immediate implementation of the 2013 WHO antiretroviraltherapy guidelines could reduce new HIV infections by 80%. Further reductions may be achieved by moving to a ‘Test andTreat’ approach, and eventually by adding a highly effective pre-exposure prophylaxis and an HIV vaccine, if they becomeavailable.
Anderson S-J, Harper M, Kilonzo N, et al., 2014, Maximising the effect of combination HIV prevention in Kenya (vol 384, pg 1426, 2014), LANCET, Vol: 384, Pages: 1576-1576, ISSN: 0140-6736
Eaton JW, Rehle TM, Jooste S, et al., 2014, Recent HIV prevalence trends among pregnant women and all women in sub-Saharan Africa: implications for HIV estimates, AIDS, Vol: 28, Pages: S507-S514, ISSN: 0269-9370
Objectives: National population-wide HIV prevalence and incidence trends in sub-Saharan Africa (SSA) are indirectly estimated using HIV prevalence measured among pregnant women attending antenatal clinics (ANC), among other data. We evaluated whether recent HIV prevalence trends among pregnant women are representative of general population trends.Design: Serial population-based household surveys in 13 SSA countries.Methods: We calculated HIV prevalence trends among all women aged 15–49 years and currently pregnant women between surveys conducted from 2003 to 2008 (period 1) and 2009 to 2012 (period 2). Log-binomial regression was used to test for a difference in prevalence trend between the two groups. Prevalence among pregnant women was age-standardized to represent the age distribution of all women.Results: Pooling data for all countries, HIV prevalence declined among pregnant women from 6.5 [95% confidence interval (CI) 5.3–7.9%] to 5.3% (95% CI 4.2–6.6%) between periods 1 and 2, whereas it remained unchanged among all women at 8.4% (95% CI 8.0–8.9%) in period 1 and 8.3% (95% CI 7.9–8.8%) in period 2. Prevalence declined by 18% (95% CI -9–38%) more in pregnant women than nonpregnant women. Estimates were similar in Western, Eastern, and Southern regions of SSA; none were statistically significant (P > 0.05). HIV prevalence decreased significantly among women aged 15–24 years while increasing significantly among women 35–49 years, who represented 29% of women but only 15% of pregnant women. Age-standardization of prevalence in pregnant women did not reconcile the discrepant trends because at older ages prevalence was lower among pregnant women than nonpregnant women.Conclusion: As HIV prevalence in SSA has shifted toward older, less-fertile women, HIV prevalence among pregnant women has declined more rapidly than prevalence in women overall. Interpretation of ANC prevalence data to inform national HIV estimates sh
Hallett TB, Zaba B, Stover J, et al., 2014, Embracing different approaches to estimating HIV incidence, prevalence and mortality, AIDS, Vol: 28, Pages: S523-S532, ISSN: 0269-9370
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- Citations: 12
Bao L, Ye J, Hallett TB, 2014, Incorporating incidence information within the UNAIDS Estimation and Projection Package framework: a study based on simulated incidence assay data, AIDS, Vol: 28, Pages: S515-S522, ISSN: 0269-9370
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- Citations: 10
Case KK, Hallett TB, Gregson S, et al., 2014, Development and future directions for the Joint United Nations Programme on HIV/AIDS estimates, AIDS, Vol: 28, Pages: S411-S414, ISSN: 0269-9370
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- Citations: 6
Vesga JF, Cori A, van Sighem A, et al., 2014, Estimating HIV incidence from case-report data: method and an application in Colombia, AIDS, Vol: 28, Pages: S489-S496, ISSN: 0269-9370
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- Citations: 7
Anderson S-J, Harper M, Kilonzo N, et al., 2014, Maximising the effect of combination HIV prevention in Kenya Reply, LANCET, Vol: 384, Pages: 1426-1427, ISSN: 0140-6736
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- Citations: 2
Dimitrov D, Boily M-C, Hallett TB, 2014, 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, Symposium on HIV Research for Prevention (HIV R4P), Publisher: MARY ANN LIEBERT, INC, Pages: A161-A161, ISSN: 0889-2229
Jones A, Cremin I, Abdullah F, et al., 2014, Transformation of HIV from pandemic to low-endemic levels: a public health approach to combination prevention, LANCET, Vol: 384, Pages: 272-279, ISSN: 0140-6736
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- Citations: 84
Anderson S-J, Cherutich P, Kilonzo N, et al., 2014, Maximising the effect of combination HIV prevention through prioritisation of the people and places in greatest need: a modelling study, The Lancet, Vol: 384, Pages: 249-256, ISSN: 0140-6736
BackgroundEpidemiological data show substantial variation in the risk of HIV infection between communities within African countries. We hypothesised that focusing appropriate interventions on geographies and key populations at high risk of HIV infection could improve the effect of investments in the HIV response.MethodsWith use of Kenya as a case study, we developed a mathematical model that described the spatiotemporal evolution of the HIV epidemic and that incorporated the demographic, behavioural, and programmatic differences across subnational units. Modelled interventions (male circumcision, behaviour change communication, early antiretoviral therapy, and pre-exposure prophylaxis) could be provided to different population groups according to their risk behaviours or their location. For a given national budget, we compared the effect of a uniform intervention strategy, in which the same complement of interventions is provided across the country, with a focused strategy that tailors the set of interventions and amount of resources allocated to the local epidemiological conditions.FindingsA uniformly distributed combination of HIV prevention interventions could reduce the total number of new HIV infections by 40% during a 15-year period. With no additional spending, this effect could be increased by 14% during the 15 years—almost 100 000 extra infections, and result in 33% fewer new HIV infections occurring every year by the end of the period if the focused approach is used to tailor resource allocation to reflect patterns in local epidemiology. The cumulative difference in new infections during the 15-year projection period depends on total budget and costs of interventions, and could be as great as 150 000 (a cumulative difference as great as 22%) under different assumptions about the unit costs of intervention.InterpretationThe focused approach achieves greater effect than the uniform approach despite exactly the same investment. Through prioritisation of
Hallett TB, Eaton JW, Menzies N, 2014, Beware of using invalid transmission models to guide HIV health policy Reply, LANCET GLOBAL HEALTH, Vol: 2, Pages: E261-E261, ISSN: 2214-109X
Martin NK, Devine A, Eaton JW, et al., 2014, MODELING THE IMPACT OF EARLY ANTIRETROVIRAL THERAPY FOR ADULTS COINFECTED WITH HIV AND HEPATITIS B OR C IN SOUTH AFRICA, 49th Annual International Liver Congress of the European-Association-for-the-Study-of-the-Liver, Publisher: ELSEVIER SCIENCE BV, Pages: S483-S483, ISSN: 0168-8278
Nayagam S, Shimakawa Y, Lemoine M, et al., 2014, FEASIBILITY AND COST ANALYSIS OF COMMUNITY BASED HEPATITIS B SCREENING PROGRAMME IN SUB-SAHARAN AFRICA, 49th Annual International Liver Congress of the European-Association-for-the-Study-of-the-Liver, Publisher: ELSEVIER SCIENCE BV, Pages: S36-S36, ISSN: 0168-8278
Smith J, Nyamukapa C, Gregson S, et al., 2014, The Distribution of Sex Acts and Condom Use within Partnerships in a Rural Sub-Saharan African Population, PLOS ONE, Vol: 9, ISSN: 1932-6203
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- Citations: 8
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