216 results found
Shubber Z, Mishra S, Vesga JF, et al., 2014, The HIV Modes of Transmission model: a systematic review of its findings and adherence to guidelines, Journal of the International AIDS Society, Vol: 17, ISSN: 1758-2652
Introduction: The HIV Modes of Transmission (MOT) model estimates the annual fraction of new HIV infections (FNI) acquired by different risk groups. It was designed to guide country-specific HIV prevention policies. To determine if the MOT produced context-specific recommendations, we analyzed MOT results by region and epidemic type, and explored the factors (e.g. data used to estimate parameter inputs, adherence to guidelines) influencing the differences.Methods: We systematically searched MEDLINE, EMBASE and UNAIDS reports, and contacted UNAIDS country directors for published MOT results from MOT inception (2003) to 25 September 2012.Results: We retrieved four journal articles and 20 UNAIDS reports covering 29 countries. In 13 countries, the largest FNI (range 26 to 63%) was acquired by the low-risk group and increased with low-risk population size. The FNI among female sex workers (FSWs) remained low (median 1.3%, range 0.04 to 14.4%), with little variability by region and epidemic type despite variability in sexual behaviour. In India and Thailand, where FSWs play an important role in transmission, the FNI among FSWs was 2 and 4%, respectively. In contrast, the FNI among men who have sex with men (MSM) varied across regions (range 0.1 to 89%) and increased with MSM population size. The FNI among people who inject drugs (PWID, range 0 to 82%) was largest in early-phase epidemics with low overall HIV prevalence. Most MOT studies were conducted and reported as per guidelines but data quality remains an issue.Conclusions: Although countries are generally performing the MOT as per guidelines, there is little variation in the FNI (except among MSM and PWID) by region and epidemic type. Homogeneity in MOT FNI for FSWs, clients and low-risk groups may limit the utility of MOT for guiding country-specific interventions in heterosexual HIV epidemics.
Jit M, Choi YH, Laprise J-F, et al., 2014, Two-dose strategies for human papillomavirus vaccination: How well do they need to protect?, VACCINE, Vol: 32, Pages: 3237-3242, ISSN: 0264-410X
Drolet M, Laprise J-F, Boily M-C, et al., 2014, Potential cost-effectiveness of the nonavalent human papillomavirus (HPV) vaccine, INTERNATIONAL JOURNAL OF CANCER, Vol: 134, Pages: 2264-2268, ISSN: 0020-7136
Boily M-C, Shubber Z, 2014, Modelling in concentrated epidemics: informing epidemic trajectories and assessing prevention approaches, CURRENT OPINION IN HIV AND AIDS, Vol: 9, Pages: 134-149, ISSN: 1746-630X
Boily M-C, Shubber Z, 2014, Modelling in concentrated epidemics: informing epidemic trajectories and assessing prevention approaches., Curr Opin HIV AIDS, Vol: 9, Pages: 134-149
PURPOSE OF THE REVIEW: This review summarizes recent mathematical modelling studies conducted among key populations including MSM, people who inject drugs (PWID), and female sex workers (FSWs) in low prevalence settings used as a marker of concentrated epidemics. RECENT FINDINGS: Most recent studies focused on MSM, Asian settings or high-income countries, studied the transmission dynamics or modelled pre-exposure prophylaxis, treatment as prevention or behavioural interventions specific to each key population (e.g., needle exchange programme or use of low-dead space syringes for PWID). Biological interventions were deemed effective and cost-effective, though still expensive, and often deemed unlikely to result in HIV elimination if used alone. Targeting high-risk individuals even within key populations improved efficiency. Some studies made innovative use of models to formally evaluate HIV prevention programmes, to interpret genetic or co-infection data, and to address methodological questions and validate epidemiological tools. CONCLUSION: More work is needed to optimize combination prevention focusing on key populations in different settings. The gaps identified include the limited number of studies modelling drug resistance, structural interventions, treatment as prevention among FSWs, and estimating the contribution of key populations to overall transmission in different settings.
Mishra S, Pickles M, Blanchard JF, et al., 2014, Distinguishing sources of HIV transmission from the distribution of newly acquired HIV infections: why is it important for HIV prevention planning?, SEXUALLY TRANSMITTED INFECTIONS, Vol: 90, Pages: 19-25, ISSN: 1368-4973
Eaton JW, Menzies NA, Stover J, et al., 2014, Health benefits, costs, and cost-effectiveness of earlier eligibility for adult antiretroviral therapy and expanded treatment coverage: a combined analysis of 12 mathematical models, LANCET GLOBAL HEALTH, Vol: 2, Pages: E23-E34, ISSN: 2214-109X
Mishra S, Mountain E, Pickles M, et al., 2014, Exploring the population-level impact of antiretroviral treatment: the influence of baseline intervention context, AIDS, Vol: 28, Pages: S61-S72, ISSN: 0269-9370
Eaton JW, Menzies NA, Stover J, et al., 2014, Health benefits, costs, and cost-effectiveness of earlier eligibility for adult antiretroviral therapy and expanded treatment coverage: a combined analysis of 12 mathematical models., Lancet Glob Health, Vol: 2, Pages: e23-e34
BACKGROUND: New WHO guidelines recommend initiation of antiretroviral therapy for HIV-positive adults with CD4 counts of 500 cells per μL or less, a higher threshold than was previously recommended. Country decision makers have to decide whether to further expand eligibility for antiretroviral therapy accordingly. We aimed to assess the potential health benefits, costs, and cost-effectiveness of various eligibility criteria for adult antiretroviral therapy and expanded treatment coverage. METHODS: We used several independent mathematical models in four settings-South Africa (generalised epidemic, moderate antiretroviral therapy coverage), Zambia (generalised epidemic, high antiretroviral therapy coverage), India (concentrated epidemic, moderate antiretroviral therapy coverage), and Vietnam (concentrated epidemic, low antiretroviral therapy coverage)-to assess the potential health benefits, costs, and cost-effectiveness of various eligibility criteria for adult antiretroviral therapy under scenarios of existing and expanded treatment coverage, with results projected over 20 years. Analyses assessed the extension of eligibility to include individuals with CD4 counts of 500 cells per μL or less, or all HIV-positive adults, compared with the previous (2010) recommendation of initiation with CD4 counts of 350 cells per μL or less. We assessed costs from a health-system perspective, and calculated the incremental cost (in US$) per disability-adjusted life-year (DALY) averted to compare competing strategies. Strategies were regarded very cost effective if the cost per DALY averted was less than the country's 2012 per-head gross domestic product (GDP; South Africa: $8040; Zambia: $1425; India: $1489; Vietnam: $1407) and cost effective if the cost per DALY averted was less than three times the per-head GDP. FINDINGS: In South Africa, the cost per DALY averted of extending eligibility for antiretroviral therapy to adult patients with CD4 counts of 500 cells per μL
Dimitrov D, Boily M-C, Brown ER, et al., 2013, Analytic Review of Modeling Studies of ARV Based PrEP Interventions Reveals Strong Influence of Drug-Resistance Assumptions on the Population-Level Effectiveness, PLOS One, Vol: 8, ISSN: 1932-6203
BackgroundFour clinical trials have shown that oral and topical pre-exposure prophylaxis (PrEP) based on tenofovir may be effective in preventing HIV transmission. The expected reduction in HIV transmission and the projected prevalence of drug resistance due to PrEP use vary significantly across modeling studies as a result of the broad spectrum of assumptions employed. Our goal is to quantify the influence of drug resistance assumptions on the predicted population-level impact of PrEP.MethodsAll modeling studies which evaluate the impact of oral or topical PrEP are reviewed and key assumptions regarding mechanisms of generation and spread of drug-resistant HIV are identified. A dynamic model of the HIV epidemic is developed to assess and compare the impact of oral PrEP using resistance assumptions extracted from published studies. The benefits and risks associated with ten years of PrEP use are evaluated under identical epidemic, behavioral and intervention conditions in terms of cumulative fractions of new HIV infections prevented, resistance prevalence among those infected with HIV, and fractions of infections in which resistance is transmitted.ResultsPublished models demonstrate enormous variability in resistance-generating assumptions and uncertainty in parameter values. Depending on which resistance parameterization is used, a resistance prevalence between 2% and 44% may be expected if 50% efficacious oral PrEP is used consistently by 50% of the population over ten years. We estimated that resistance may be responsible for up to a 10% reduction or up to a 30% contribution to the fraction of prevented infections predicted in different studies.ConclusionsResistance assumptions used in published studies have a strong influence on the projected impact of PrEP. Modelers and virologists should collaborate toward clarifying the set of resistance assumptions biologically relevant to the PrEP products which are already in use or soon to be added to the arsenal against
Pickles M, Boily M-C, Vickerman P, et al., 2013, Assessment of the population-level effectiveness of the Avahan HIV-prevention programme in South India: a preplanned, causal-pathway-based modelling analysis, LANCET GLOBAL HEALTH, Vol: 1, Pages: E289-E299, ISSN: 2214-109X
Behanzin L, Diabate S, Minani I, et al., 2013, Assessment of HIV-related risky behaviour: a comparative study of face-to-face interviews and polling booth surveys in the general population of Cotonou, Benin, SEXUALLY TRANSMITTED INFECTIONS, Vol: 89, Pages: 595-601, ISSN: 1368-4973
Owen BN, Brock PM, Shubber Z, et al., 2013, 31. Lifetime prevalence of anal intercourse among sexually active female youth and young female sex workers: a comparative systematic review and meta-analysis., ISSN: 1448-5028
Background Anal cancer incidence has increased over the past twenty years. Heterosexual anal intercourse (AI) is a risk factor for HPV and HIV infection but is under-researched and ill-understood. We compare AI practices among young, sexually active general population females and female sex workers (FSW). Methods: We searched PubMed for heterosexual AI studies among young females, including FSWs (mean age <25 years), to December 2012. Study estimates were pooled using a random-effects model. Results: Fifty-four studies (42 average-risk, 6 higher-risk, 6 FSWs) were included. Most studies among general population youth were conducted in North America using self-administered questionnaires. All FSW studies were conducted in Africa and Asia using face-to-face interviews (FTFI). Pooled estimates of lifetime AI prevalence were larger among average-risk (23.6%, 95% CI 20.4-26.7) and higher-risk youth (25.5%, 95% CI 11.7-39.2) than FSWs (12.8%, 95% CI 8.4-17.3), but highly heterogeneous (I2 >90%). However, pooled AI estimates by continent of average-risk youth (Asia=13.9%, 95% CI=1.7-29.5; Africa=18.4%, 95% CI 0.9-35.8) were more similar to those of FSWs (Asia=16.0%, 95% CI 10.3-21.6; Africa=9.7%, 95% CI 3.8-15.7). Estimates of average-risk youth reporting via FTFI (12.1%, 95% CI 0.7-23.5) were likewise similar to those among FSWs (12.8%, 95% CI 8.4-17.3). Pooled AI prevalence estimates among FSWs were higher in studies conducted after 2001 than in earlier studies. Conclusions: AI is common among sexually active females and may be increasing; it could therefore be an important determinant of HPV transmission and anal cancers. AI is as or more common among the general population youth than young FSWs but this may be confounded by continent, interview method and other unmeasured variables.
Dimitrov D, Boily M-C, Marrazzo J, et al., 2013, Population-Level Benefits from Providing Effective HIV Prevention Means to Pregnant Women in High Prevalence Settings, PLOS One, Vol: 8, ISSN: 1932-6203
BackgroundHIV prevalence among pregnant women in Southern Africa is extremely high. Epidemiological studies suggest that pregnancy increases the risk of HIV sexual acquisition and that HIV infections acquired during pregnancy carry higher risk of mother-to-child transmission (MTCT). We analyze the potential benefits from extending the availability of effective microbicide to pregnant women (in addition to non-pregnant women) in a wide-scale intervention.Methods and FindingsA transmission dynamic model was designed to assess the impact of microbicide use in high HIV prevalence settings and to estimate proportions of new HIV infections, infections acquired during pregnancy, and MTCT prevented over 10 years. Our analysis suggests that consistent use of microbicide with 70% efficacy by 60% of non-pregnant women may prevent approximately 40% and 15% of new infections in women and men respectively over 10 years, assuming no additional increase in HIV risk to either partner during pregnancy (RRHIV/preg = 1). It may also prevent 8–15% MTCT depending on the increase in MTCT risk when HIV is acquired during pregnancy compared to before pregnancy (RRMTCT/preg). Extending the microbicides use during pregnancy may improve the effectiveness of the intervention by 10% (RRHIV/preg = 1) to 25% (RRHIV/preg = 2) and reduce the number of HIV infections acquired during pregnancy by 40% to 70% in different scenarios. It may add between 6% (RRHIV/preg = 1, RRMTCT/preg = 1) and 25% (RRHIV/preg = 2, RRMTCT/preg = 4) to the reduction in the residual MTCT.ConclusionProviding safe and effective microbicide to pregnant women in the context of wide-scale interventions would be desirable as it would increase the effectiveness of the intervention and significantly reduce the number of HIV infections acquired during pregnancy. The projected benefits from covering pregnant women by the HIV prevention programs is more substantial in communities in which the sexual risk during pregnancy is eleva
Brisson M, Laprise J-F, Drolet M, et al., 2013, Comparative cost-effectiveness of the quadrivalent and bivalent human papillomavirus vaccines: A transmission-dynamic modeling study, VACCINE, Vol: 31, Pages: 3863-3871, ISSN: 0264-410X
Dimitrov D, Boily MC, Mâsse BR, et al., 2013, Impact of pill sharing on drug resistance due to a wide-scale oral prep intervention in generalized epidemics, Journal of AIDS and Clinical Research, Vol: 4
Background: The first antiretroviral drug (Truvada) to be used as a pre-exposure prophylaxis (PrEP) in preventing HIV transmission is about to be approved. Behavioral studies suggest that a portion of users may share anti-retroviral drugs with sex partners, family, or friends. Pill sharing will decrease PrEP efficacy and adherence level, and potentially create an environment favorable for the development of drug resistance. We aim to evaluate the potential impact of pill sharing on the PrEP effectiveness and on the rates of drug-resistance development in heterosexual populations. Methods: A transmission dynamic model was used to assess the population-level impact of oral PrEP. The fractions of new HIV infections prevented (CPF), drug resistance prevalence and the proportion of new infections in which drug-resistant HIV is transmitted (TDR) are evaluated over fixed time periods. The influence of different factors on CPF and TDR is studied through simulations, using epidemic parameters representative of the countries in Sub-Saharan Africa. Results: Without pill sharing, a 70% efficacious PrEP used consistently by 60% of uninfected individuals prevents 52.8% (95% CI 49.4%-56.4%) of all new HIV infections over ten years with drug-resistant HIV transmitted in 2.2% of the new infections. Absolute CPF may vary by 9% if up to 20% of the users share PrEP while the level of TDR and total resistance prevalence may increase by up to 6-fold due to pill sharing in some intervention scenarios. Conclusion: Pill sharing may increase the PrEP coverage level achieved in the population but it also affects the PrEP efficacy for the users who do not follow the prescribed schedule. More importantly, it creates a pool of untracked users who remain unreached by the effort to avoid sub-optimal PrEP usage by infected people. This increases substantially the potential risk of drug resistance in the population. © 2012 Dimitrov D, et al.
Shubber Z, Mishra S, Vesga JF, et al., 2013, THE HIV MODES OF TRANSMISSION MODEL: A SYSTEMATIC REVIEW OF ITS FINDINGS AND ADHERENCE TO GUIDELINES, SEXUALLY TRANSMITTED INFECTIONS, Vol: 89, Pages: A52-A52, ISSN: 1368-4973
Vesga JF, Boily MC, Hallett TB, 2013, ESTIMATING THE IMPACT OF ANTIRETROVIRAL THERAPY AND CONDOMS IN THE HIV EPIDEMIC OF BOGOTA, COLOMBIA, SEXUALLY TRANSMITTED INFECTIONS, Vol: 89, Pages: A281-A281, ISSN: 1368-4973
Tavitian-Exley I, Boily MC, Vickerman P, 2013, HIV RISK IN PEOPLE WHO INJECT DIFFERENT DRUGS: SYSTEMATIC REVIEW AND META-ANALYSIS, SEXUALLY TRANSMITTED INFECTIONS, Vol: 89, Pages: A179-A179, ISSN: 1368-4973
Drolet M, Boily M-C, Van de Velde N, et al., 2013, Vaccinating Girls and Boys with Different Human Papillomavirus Vaccines: Can It Optimise Population-Level Effectiveness?, PLOS One, Vol: 8, ISSN: 1932-6203
BackgroundDecision-makers may consider vaccinating girls and boys with different HPV vaccines to benefit from their respective strengths; the quadrivalent (HPV4) prevents anogenital warts (AGW) whilst the bivalent (HPV2) may confer greater cross-protection. We compared, to a girls-only vaccination program with HPV4, the impact of vaccinating: 1) both genders with HPV4, and 2) boys with HPV4 and girls with HPV2.MethodsWe used an individual-based transmission-dynamic model of heterosexual HPV infection and diseases. Our base-case scenario assumed lifelong efficacy of 100% against vaccine types, and 46,29,8,18,6% and 77,43,79,8,0% efficacy against HPV-31,-33,-45,-52,-58 for HPV4 and HPV2, respectively.ResultsAssuming 70% vaccination coverage and lifelong cross-protection, vaccinating boys has little additional benefit on AGW prevention, irrespective of the vaccine used for girls. Furthermore, using HPV4 for boys and HPV2 for girls produces greater incremental reductions in SCC incidence than using HPV4 for both genders (12 vs 7 percentage points). At 50% vaccination coverage, vaccinating boys produces incremental reductions in AGW of 17 percentage points if both genders are vaccinated with HPV4, but increases female incidence by 16 percentage points if girls are switched to HPV2 (heterosexual male incidence is incrementally reduced by 24 percentage points in both scenarios). Higher incremental reductions in SCC incidence are predicted when vaccinating boys with HPV4 and girls with HPV2 versus vaccinating both genders with HPV4 (16 vs 12 percentage points). Results are sensitive to vaccination coverage and the relative duration of protection of the vaccines.ConclusionVaccinating girls with HPV2 and boys with HPV4 can optimize SCC prevention if HPV2 has higher/longer cross-protection, but can increase AGW incidence if vaccination coverage is low among boys.
Boily M-C, Pickles M, Lowndes CM, et al., 2013, Positive impact of a large-scale HIV prevention programme among female sex workers and clients in South India, AIDS, Vol: 27, Pages: 1449-1460, ISSN: 0269-9370
Brisson M, Drolet M, Boily M-C, et al., 2013, RE: Population-Level Impact of the Bivalent, Quadrivalent, and Candidate Nonavalent Human Papillomavirus Vaccines: A Comparative Model-Based Analysis Response, JNCI-JOURNAL OF THE NATIONAL CANCER INSTITUTE, Vol: 105, Pages: 664-665, ISSN: 0027-8874
Boily M-C, Brisson M, Drolet M, et al., 2013, RE: Annual Report to the Nation on the Status of Cancer, 1975-2009, Featuring the Burden and Trends in Human Papillomavirus (HPV)-Associated Cancers and HPV Vaccination Coverage Levels and RE: Inequalities in Human Papillomavirus (HPV)-Associated Cancers: Implications for the Success of HPV Vaccination Response, JNCI-JOURNAL OF THE NATIONAL CANCER INSTITUTE, Vol: 105, Pages: 750-751, ISSN: 0027-8874
Phillips AE, Molitor J, Boily MC, et al., 2013, Informal confidential voting interviewing in a sexual risk assessment of men who have sex with men (MSM) and transgenders (hijra) in Bangalore, India, SEXUALLY TRANSMITTED INFECTIONS, Vol: 89, Pages: 245-250, ISSN: 1368-4973
Behanzin L, Diabate S, Minani I, et al., 2013, Decline in the Prevalence of HIV and Sexually Transmitted Infections Among Female Sex Workers in Benin Over 15 Years of Targeted Interventions, JAIDS-JOURNAL OF ACQUIRED IMMUNE DEFICIENCY SYNDROMES, Vol: 63, Pages: 126-134, ISSN: 1525-4135
Drolet M, Boily M-C, Greenaway C, et al., 2013, Sociodemographic Inequalities in Sexual Activity and Cervical Cancer Screening: Implications for the Success of Human Papillomavirus Vaccination, CANCER EPIDEMIOLOGY BIOMARKERS & PREVENTION, Vol: 22, Pages: 641-652, ISSN: 1055-9965
Malagon T, Joumier V, Boily M-C, et al., 2013, The impact of differential uptake of HPV vaccine by sexual risks on health inequalities: A model-based analysis, VACCINE, Vol: 31, Pages: 1740-1747, ISSN: 0264-410X
Baggaley RF, Dimitrov D, Owen BN, et al., 2013, Heterosexual Anal Intercourse: A Neglected Risk Factor for HIV?, AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Vol: 69, Pages: 95-105, ISSN: 1046-7408
Deering KN, Bhattacharjee P, Mohan HL, et al., 2013, Violence and HIV Risk Among Female Sex Workers in Southern India, SEXUALLY TRANSMITTED DISEASES, Vol: 40, Pages: 168-174, ISSN: 0148-5717
Bradley J, Rajaram S, Moses S, et al., 2013, Female Sex Worker Client Behaviors Lead to Condom Breakage: A Prospective Telephone-Based Survey in Bangalore, South India, AIDS AND BEHAVIOR, Vol: 17, Pages: 559-567, ISSN: 1090-7165
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