Imperial College London

ProfessorMarie-ClaudeBoily

Faculty of MedicineSchool of Public Health

Professor of Mathematical Epidemiology
 
 
 
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Contact

 

+44 (0)20 7594 3263mc.boily

 
 
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Location

 

LG26Norfolk PlaceSt Mary's Campus

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Summary

 

Publications

Publication Type
Year
to

216 results found

Stannah J, Silhol R, Elmes J, Owen B, Shacklett BL, Anton P, McGowan I, van der Straten A, Dimitrov D, Baggaley RF, Boily M-Cet al., 2019, Increases in HIV incidence following receptive anal intercourse among women: A systematic review and meta-analysis., AIDS and Behavior, Pages: 1-15, ISSN: 1090-7165

Receptive anal intercourse (RAI) carries a greater per-act risk of HIV acquisition than receptive vaginal intercourse (RVI) and may influence HIV epidemics driven by heterosexual sex. This systematic review explores the association between RAI and incident HIV among women, globally. We searched Embase and Medline through September 2018 for longitudinal studies reporting crude (cRR) or adjusted (aRR) relative risks of HIV acquisition by RAI practice among women. Of 27,563 articles identified, 17 eligible studies were included. We pooled independent study estimates using random-effects models. Women reporting RAI were more likely to acquire HIV than women not reporting RAI (pooled cRR = 1.56 95% CI 1.03-2.38, N = 18, I2 = 72%; pooled aRR = 2.23, 1.01-4.92, N = 5, I2 = 70%). In subgroup analyses the association was lower for women in Africa (pooled cRR = 1.16, N = 13, I2 = 21%) than outside Africa (pooled cRR = 4.10, N = 5, I2 = 79%) and for high-risk (pooled aRR = 1.69, N = 4, I2 = 63%) than general-risk women (pooled aRR = 8.50, N = 1). Interview method slightly influenced cRR estimates (p value = 0.04). In leave-one-out sensitivity analyses pooled estimates were generally robust to removing individual study estimates. Main limitations included poor exposure definition, incomplete adjustment for confounders, particularly condom use, and use of non-confidential interview methods. More and better data are needed to explain differences in risk by world region and risk population. Women require better counselling and greater choice in prevention modalities that are effective during RVI and RAI.

Journal article

Dimitrov D, Moore J, Wood D, Mitchell K, Li M, Hughes J, Donnell D, Mannheimer S, Holtz T, Grant R, Boily MCet al., Predicted effectiveness of daily and non-daily PrEP for MSM based on sex and pill-taking patterns from HPTN 067/ADAPT, Clinical Infectious Diseases, ISSN: 1058-4838

Background: HPTN 067/ADAPT evaluated the feasibility of daily and non-daily HIV pre-exposure prophylaxis (PrEP) regimens among high-risk populations, including men who have sex with men (MSM) and transgender women, in Bangkok, Thailand and Harlem, New York, U.S. We used a mathematical model to predict the efficacy and effectiveness of different dosing regimens. Methods: An individual-based mathematical model was used to simulate annual HIV incidence among MSM cohorts. PrEP efficacy for covered sex acts, as defined in the HPTN 067/ADAPT protocol, was estimated using subgroup efficacy estimates from the iPrEx trial. Effectiveness was estimated by comparison of the HIV incidence with and without PrEP use.Results: We estimated that PrEP was highly protective (85%–96% efficacy across regimens and sites) for fully covered acts. PrEP was more protective for partially covered acts in Bangkok (71%–88% efficacy) than in Harlem (62%–81% efficacy). Our model projects 80%, 62%, and 68% effectiveness of daily, time-driven, and event-driven PrEP for MSM in Harlem compared with 90%, 85% and 79% for MSM in Bangkok. Halving the efficacy for partially covered acts decreases effectiveness by 8–9 percentage points in Harlem and by 5–9 percentage points in Bangkok across regimens. Conclusions: Our analysis suggests that PrEP was more effective among MSM in Thailand than in the U.S. as a result of more fully covered sex acts and more pills taken around partially covered acts. Overall, non-daily PrEP was less effective than daily PrEP, especially in the U.S. where the sex act coverage associated with daily use was substantially higher.

Journal article

Drolet M, Benard E, Perez N, Boily M-C, Hammad A, Baldo V, Brassard P, Brotherton J, Callandar D, Checchi M, Chow E, Cocchio S, Dalianis T, Deeks S, Dehlendorff C, Donovan B, Fairley C, Flagg E, Gargano J, Garland S, Grun N, Hansen B, Harrison C, Herweijer E, Imburgia T, Johnson A, Kahn J, Brisson Met al., 2019, Population-level impact and herd effects following the introduction of human papillomavirus vaccination programs: updated systematic review and meta-analysis, Lancet, Vol: 394, Pages: 497-509, ISSN: 0140-6736

BackgroundMore than ten years have elapsed since human papillomavirus (HPV) vaccination was implemented. We performed a systematic review and meta-analysis of the population-level impact of female-only HPV vaccination on HPV infections, anogenital wart diagnoses (AGW) and cervical intraepithelial neoplasia grade 2+ (CIN2+) to summarise the most recent evidence about the effectiveness of HPV vaccines in real-world settings and to quantify the impact of multiple age-cohort vaccination.MethodsWe updated our prior review (01/01/2007–28/02/2014), by searching Medline and Embase (01/02/2014–11/10/2018) for studies that examined changes, between pre- and post-vaccination periods, in HPV infections, AGW, or CIN2+. We stratified all analyses by sex, age, and years since HPV vaccination introduction. We used random-effects models to estimate pooled relative risks and performed subgroup analysis to identify the main sources of heterogeneity. FindingsWe identified 65 eligible articles conducted in 14 high-income countries. After 5-8 years of vaccination, HPV-16/18, AGW, and CIN2+ decreased significantly by about 80%, 70%, and 50% among girls aged 15-19 years and by 65%, 55%, and 30% among women aged 20-24 years. Significant cross-protection and herd effects were also observed. HPV-31/33/45 decreased significantly by 50% among girls aged 15-19 years and AGW decreased significantly by 30-50% among boys/men aged 15-24 years. After 5-8 years of vaccination, countries with multi-cohort vaccination and high coverage (≥50%) had greater reductions in AGW, 44 and 85 percentage points among girls and boys aged 15-19 years, respectively, than countries with single-cohort vaccination and/or low vaccination coverage. InterpretationOur meta-analysis, including data from >60 million individuals from 14 high-income countries, shows a substantial impact of female-only HPV vaccination programs on AGW among girls/women and boys/men, and HPV infections and CIN2+ among girls/women

Journal article

Stannah J, Dale E, Elmes J, Staunton R, Beyrer C, Mitchell K, Boily M-Cet al., HIV testing and engagement with the HIV treatment cascade among men who have sex with men in Africa: A systematic review and meta-analysis, Lancet HIV, ISSN: 2405-4704

BackgroundHIV disproportionately affects gay, bisexual, and other men who have sex with men (MSM) in Africa, where many countries criminalise same-sex behaviour. We assessed changes in the engagement of African MSM with HIV testing and treatment cascade stages over time, and the influence of anti-LGBT legislation and stigma.MethodsWe systematically searched the peer-reviewed literature to October 10th , 2018 for studies and extracted or derived estimates of HIV testing and/or engagement with the HIV treatment cascade among African MSM from published reports. We derived pooled estimates using inverse-variance random-effects models. We used subgroup and meta-regression analysis to assess associations between testing and status awareness outcomes and study and participant characteristics including the severity of country-level anti-LGBT legislation.FindingsOur searches identified 75 independent eligible studies that provided estimates for 44,993 MSM across one or more of five testing and treatment cascade outcomes. HIV testing increased significantly over time overall, with pooled overall proportions of MSM ever tested of 67·3% (95%Confidence interval 62·1-72·3%,N=44) and tested in the past 12 months of 50·1% (42·4-57·8%,N=31) post-2011 – 14% and 18% points higher than pre-2011, respectively. Post-2011, ever testing was highest in Southern(80·0%) and lowest in Northern(34·4%) and Central(56·1%) Africa, with the greatest increase in Western Africa(from 42·4 to 70·9%). Levels of both testing outcomes and status awareness were statistically significantly lower in countries with the most severe anti-LGBT legislation.Few estimates were available for later stages of the treatment cascade. Available data post61 2011 suggest that the pooled proportion of MSM HIV-positive aware has remained low (18·5%, 12·5-25·3%,N=28) whereas proportions of current ART use were 23·7%

Journal article

Maheu-Giroux M, Diabate S, Boily M-C, Jean-Paul N, Vesga J, Baral S, Abo K, Wognin V, Diouf D, Alary Met al., 2019, Cost-effectiveness of accelerated HIV response scenarios in Côte d’Ivoire, JAIDS-Journal of Acquired Immune Deficiency Syndromes, Vol: 80, Pages: 503-512, ISSN: 1525-4135

Background: Despite Côte d’Ivoire epidemic being labelled as ‘generalized’, key populations (KP) are important to overall transmission. Using a dynamic model of HIV transmission, we previously estimated the impact of several treatment-as-prevention strategies that reached –or missed– the UNAIDS 90-90-90 targets in different populations groups, including KP and clients of female sex workers (CFSW). To inform program planning and resources allocation, we assessed the cost-effectiveness of these scenarios.Methods: Costing was performed from the provider’s perspective. Unit costs were obtained from the Ivorian Programme national de lutte contre le Sida (USD 2015) and discounted at 3%. Net incremental cost-effectiveness ratios (ICER) per adult HIV infection prevented and per disability-adjusted life years (DALY) averted were estimated over 2015-2030.Results: The three most cost-effective and affordable scenarios were the ones that projected current programmatic trends (ICER=$210; 90% uncertainty interval [90UI%]: $150-$300), attaining the 90-90-90 objectives among KP and CFSW (ICER=$220; 90%UI: $80-$510), and among KP only (ICER=$290; 90%UI: $90-$660). The least cost-effective scenario was the one that reached the UNAIDS 90-90-90 target accompanied by a 25% point drop in condom use in KP (ICER=$710; 90%UI: $450-$1,270). In comparison, the UNAIDS scenario had a net ICER of $570 (90%UI: $390-$900) per DALY averted.Conclusions: According to commonly used thresholds, accelerating the HIV response can be considered very cost-effective for all scenarios. However, when balancing epidemiological impact, cost-effectiveness, and affordability, scenarios that sustain both high condom use and rates of viral suppression among KP and CFSW appear most promising in Côte d’Ivoire.

Journal article

Owen BN, Baggaley RF, Elmes J, Harvey A, Shubber Z, Butler AR, Silhol R, Anton P, Shacklett B, van der Straten A, Boily MCet al., 2019, What proportion of female sex workers practise anal intercourse and how frequently? A systematic review and meta-analysis, AIDS and Behavior, ISSN: 1090-7165

HIV is more efficiently acquired during receptive anal intercourse (AI) compared to vaginal intercourse (VI) and may contribute substantially to female sex workers’ (FSW) high HIV burden. We aim to determine how common and frequent AI is among FSW globally. We searched PubMed, Embase and PsycINFO for studies reporting the proportion of FSW practising AI (prevalence) and/or the number of AI acts (frequency) worldwide from 01/1980 to 10/2018. We assessed the influence of participant and study characteristics on AI prevalence (e.g. continent, study year and interview method) through sub-group analysis. Of 15,830 identified studies, 131 were included. Nearly all (N = 128) reported AI prevalence and few frequency (N = 13), over various recall periods. Most studies used face-to-face interviews (N = 111). Pooled prevalences varied little by recall period (lifetime: 15.7% 95%CI 12.2–19.3%, N = 30, I 2 = 99%; past month: 16.2% 95%CI 10.8–21.6%, N = 18, I 2 = 99%). The pooled proportion of FSW reporting < 100% condom use tended to be non-significantly higher during AI compared to during VI (e.g. any unprotected VI: 19.1% 95%CI 1.7–36.4, N = 5 and any unprotected AI: 46.4% 95%CI 9.1–83.6, N = 5 in the past week). Across all study participants, between 2.4 and 15.9% (N = 6) of all intercourse acts (AI and VI) were anal. Neither AI prevalence nor frequency varied substantially by any participant or study characteristics. Although varied, AI among FSW is generally common, inconsistently protected with condoms and practiced sufficiently frequently to contribute substantially to HIV acquisition in this risk group. Interventions to address barriers to condom use are needed.

Journal article

Mitchell KM, Hoots B, German D, FLynn C, Farley J, Gelman M, Hughes J, DOnnell D, Adeyeye A, Remien R, Beyrer C, Paz Bailey G, Boily M-Cet al., 2019, Improvements in the HIV care continuum needed to meaningfully reduce HIV incidence among men who have sex with men in Baltimore, US: a modelling study for HPTN 078, Journal of the International AIDS Society, Vol: 22, ISSN: 1758-2652

Introduction HIV prevalence is high among men who have sex with men (MSM) in Baltimore, Maryland, United States, and levels of viral suppression among HIV-positive MSM are relatively low. The HIV Prevention Trials Network (HPTN) 078 trial seeks to increase levels of viral suppression among US MSM by increasing rates of diagnosis and linkage to care and treatment. We estimated the increases in viral suppression needed to reach different HIV incidence reduction targets, and the impact of meeting diagnosis and treatment targets.Methods: We used a mathematical model of HIV transmission among MSM from Baltimore, US, parameterised with behavioural data and fitted to HIV prevalence and care continuum data for Baltimore wherever possible, to project increases in viral suppression needed to reduce the HIV incidence rate among Baltimore MSM by 10, 20, 30, or 50% after 2, 5, and 10 years. We also projected HIV incidence reductions achieved if US national targets – 90% of people living with HIV (PLHIV) know their HIV serostatus, 90% of those diagnosed are retained in HIV medical care and 80% of those diagnosed are virally suppressed - or UNAIDS 90-90-90 targets (90% of PLHIV know their status, 90% of those diagnosed receive antiretroviral therapy (ART), 90% of those receiving ART are virally suppressed) are each met by 2020.Results: To reduce the HIV incidence rate by 20% and 50% after 5 years (compared with the base-case at the same time point), the proportion of all HIV-positive MSM who are virally suppressed must increase above 2015 levels by a median 13 percentage points (95% uncertainty interval 9-16 percentage points) from median 49% to 60%, and 27 percentage points (22-35) from 49% to 75%, respectively. Meeting all three US or 90-90-90 UNAIDS targets results in a 48% (31-63%) and 51% (38-65%) HIV incidence rate reduction in 2020, respectively. Conclusions: Substantial improvements in levels of viral suppression will be needed to achieve significant incidence reduct

Journal article

Baggaley R, Owen B, Silhol R, Elmes J, Anton P, McGowan I, van der Straten A, Shacklett B, Dang Q, Swann EM, Bolton DL, Boily MCet al., 2018, Does per-act HIV-1 transmission risk through anal sex vary by gender? An updated systematic review and meta-analysis, American Journal of Reproductive Immunology, Vol: 80, ISSN: 1046-7408

Quantifying HIV‐1 transmission risk per‐act of anal intercourse (AI) is important for HIV‐1 prevention. We updated previous reviews by searching Medline and Embase to 02/2018. We derived pooled estimates of receptive AI (URAI) and insertive AI (UIAI) risk unprotected by condoms using random‐effects models. Subgroup analyses were conducted by gender, study design, and whether antiretroviral treatment (ART) had been introduced by the time of the study. Two new relevant studies were identified, one of which met inclusion criteria, adding three new cohorts and increasing number of individuals/partnerships included from 1869 to 14 277. Four studies, all from high‐income countries, were included. Pooled HIV‐1 risk was higher for URAI (1.25%, 95% CI 0.55%‐2.23%, N = 5, I2 = 87%) than UIAI (0.17%, 95 % CI 0.09%‐0.26%, N = 3, I2 = 0%). The sole heterosexual URAI estimate (3.38%, 95% CI 1.85%‐4.91%), from a study of 72 women published in a peer‐reviewed journal, was significantly higher than the men‐who‐have‐sex‐with‐men (MSM) pooled estimate (0.75%, 95% CI 0.56%‐0.98%, N = 4, P < 0.0001) and higher than the only other heterosexual estimate identified (0.4%, 95% CI 0.08%‐2.0%, based on 59 women, excluded for being a pre‐2013 abstract). Pooled per‐act URAI risk varied by study design (retrospective‐partner studies: 2.56%, 95% CI 1.20%‐4.42%, N = 2 (one MSM, one heterosexual); prospective studies: 0.71%, 95% CI 0.51%‐0.93%, N = 3 MSM, P < 0.0001). URAI risk was lower for studies conducted in the ART era (0.75%, 95% CI 0.52%‐1.03%) than pre‐ART (1.67%, 95% CI 0.44%‐3.67%) but not significantly so (P = 0.537). Prevention messages must emphasize that HIV‐1 infectiousness through AI remains high, even in the ART era. Further studies, particularly among heterosexual populations and in resource‐limited settings, are required to elucidate whether AI risk differs by gender, region and following population‐level ART scale‐up.

Journal article

Mboup A, Behanzin L, Guedou FA, Geraldo N, Goma-Matsetse E, Giguere K, Aza-Gnandji M, Kessou L, Diallo M, Keke RK, Bachabi M, Dramane K, Geidelberg L, Cianci F, Lafrance C, Affolabi D, Diabate S, Gagnon M-P, Zannou DM, Gangbo F, Boily M-C, Vickerman P, Alary Met al., 2018, Early antiretroviral therapy and daily pre-exposure prophylaxis for HIV prevention among female sex workers in Cotonou, Benin: a prospective observational demonstration study, Journal of the International AIDS Society, Vol: 21, ISSN: 1758-2652

IntroductionIn sub‐Saharan Africa, HIV prevalence remains high, especially among key populations. In such situations, combination prevention including clinical, behavioural, structural and biological components, as well as adequate treatment are important. We conducted a demonstration project at the Dispensaire IST, a clinic dedicated to female sex workers (FSWs) in Cotonou, on early antiretroviral therapy (E‐ART, or immediate “test‐and‐treat”) and pre‐exposure prophylaxis (PrEP). We present key indicators such as uptake, retention and adherence.MethodsIn this prospective observational study, we recruited FSWs from October 4th 2014 to December 31st 2015 and followed them until December 31st 2016. FSWs were provided with daily tenofovir disoproxil fumarate/emtricitabine (Truvada®) for PrEP or received a first‐line antiretroviral regimen as per Benin guidelines. We used generalized estimating equations to assess trends in adherence and sexual behaviour.ResultsAmong FSWs in the catchment area, HIV testing coverage within the study framework was 95.5% (422/442). At baseline, HIV prevalence was 26.3% (111/422). Among eligible FSWs, 95.5% (105/110) were recruited for E‐ART and 88.3% (256/290) for PrEP. Overall retention at the end of the study was 59.0% (62/105) for E‐ART and 47.3% (121/256) for PrEP. Mean (±SD) duration of follow‐up was 13.4 (±7.9) months for E‐ART and 11.8 (±7.9) months for PrEP. Self‐reported adherence was over 90% among most E‐ART participants. For PrEP, adherence was lower and the proportion with 100% adherence decreased over time from 78.4% to 56.7% (p‐trend < 0.0001). During the 250.1 person‐years of follow‐up among PrEP initiators, two seroconversions occurred (incidence 0.8/100 person‐years (95% confidence interval: 0.3 to 1.9/100 person‐years)). The two seroconverters had stopped using PrEP for at least six months before being found HIV‐infected. In both groups, there was no evidence of reduced condom use.

Journal article

Borquez A, Beletsky L, Nosyk B, Strathdee SA, Madrazo A, Abramovitz D, Rafful C, Morales M, Cepeda J, Panagiotoglou D, Krebs E, Vickerman P, Boily MC, Thomson N, Martin NKet al., 2018, The effect of public health-oriented drug law reform on HIV incidence in people who inject drugs in Tijuana, Mexico: an epidemic modelling study, Lancet Public Health, Vol: 3, Pages: e429-e437, ISSN: 2468-2667

BackgroundAs countries embark on public health-oriented drug law reform, health impact evaluations are needed. In 2012, Mexico mandated the narcomenudeo reform, which depenalised the possession of small amounts of drugs and instituted drug treatment instead of incarceration. We investigated the past and future effect of this drug law reform on HIV incidence in people who inject drugs in Tijuana, Mexico.MethodsIn this epidemic modelling study, we used data from the El Cuete IV cohort study to develop a deterministic model of injecting and sexual HIV transmission in people who inject drugs in Tijuana between 2012 and 2030. The population was stratified by sex, incarceration status, syringe confiscation by the police, HIV stage, and exposure to drug treatment or rehabilitation (either opioid agonist treatment or compulsory drug abstinence programmes). We modelled the effect of these exposures on HIV risk in people who inject drugs, estimating the effect of observed and potential future reform enforcement levels.FindingsIn 2011, prior to the narcomenudeo reform, 547 (75%) of 733 people who inject drugs in the El Cuete cohort reported having ever been incarcerated, on average five times since starting injecting. Modelling estimated the limited reform implementation averted 2% (95% CI 0·2–3·0) of new HIV infections in people who inject drugs between 2012 and 2017. If implementation reduced incarceration in people who inject drugs by 80% from 2018 onward, 9% (95% CI 4–16) of new HIV infections between 2018 and 2030 could be averted, with 21% (10–33) averted if people who inject drugs were referred to opioid agonist treatment instead of being incarcerated. Referral to compulsory drug abstinence programmes instead of prison could have a lower or potentially negative impact with −2% (95% CI −23 to 9) infections averted.InterpretationMexican drug law reform has had a negligible effect on the HIV epidemic among people who inject drugs

Journal article

Shannon K, Crago A-L, Baral S, Bekker L-G, Kerrigan D, Decker M, Poteat T, Wirtz A, Weir B, Boily MC, Butler J, Strathdee S, Beyrer Cet al., 2018, The global response and unmet actions for HIV and sex workers, Lancet, Vol: 392, Pages: 698-710, ISSN: 0140-6736

Female, male, and transgender sex workers continue to have disproportionately high burdens of HIV infection in low-income, middle-income, and high-income countries in 2018. 4 years since our Lancet Series on HIV and sex work, our updated analysis of the global HIV burden among female sex workers shows that HIV prevalence is unacceptably high at 10·4% (95% CI 9·5–11·5) and is largely unchanged. Comprehensive epidemiological data on HIV and antiretroviral therapy (ART) coverage are scarce, particularly among transgender women. Sustained coverage of treatment is markedly uneven and challenged by lack of progress on stigma and criminalisation, and sustained human rights violations. Although important progress has been made in biomedical interventions with pre-exposure prophylaxis and early ART feasibility and demonstration projects, limited coverage and retention suggest that sustained investment in community and structural interventions is required for sex workers to benefit from the preventive interventions and treatments that other key populations have. Evidence-based progress on full decriminalisation grounded in health and human rights—a key recommendation in our Lancet Series—has stalled, with South Africa a notable exception. Additionally, several countries have rolled back rights to sex workers further. Removal of legal barriers through the decriminalisation of sex work, alongside political and funding investments to support community and structural interventions, is urgently needed to reverse the HIV trajectory and ensure health and human rights for all sex workers.

Journal article

Mukandavire C, Walker J, Schwartz S, Boily MC, Marie-Claude B, Leon D, Carrie L, Daouda D, Ben L, Nafissatou Leye D, Fatou D, Karleen C, Remy Serge MM, Safiatou T, Papa Amadou Niang D, Coumba T, Cheikh N, Erik V, Sharmistha M, Stefan B, Peter Vet al., 2018, Estimating the contribution of key populations towards spread of HIV in Dakar, Senegal, Journal of the International AIDS Society, Vol: 21, ISSN: 1758-2652

IntroductionKey populations including female sex workers (FSW) and men who have sex with men (MSM) bear a disproportionate burden of HIV. However, the role of focusing prevention efforts on these groups for reducing a country’s HIV epidemic is debated. We estimate the extent to which HIV transmission amongst FSW and MSM contributes to overall HIV transmission in Dakar, Senegal, using a dynamic assessment of the population attributable fraction (PAF).MethodsA dynamic transmission model of HIV among FSW, their clients, MSM and the lower-risk adult population was parameterized and calibrated within a Bayesian framework using setting-specific demographic, behavioural, HIV epidemiological, and antiretroviral treatment (ART) coverage data for 1985-2015. We used the model to estimate the 10-year PAF of commercial sex between FSW and their clients, and sex between men, to overall HIV transmission (defined as the percentage of new infections prevented when these modes of transmission are removed). Additionally, we estimated the prevention benefits associated with historical increases in condom use and ART uptake, and impact of further increases in prevention and treatment.ResultsThe model projections suggest that unprotected sex between men contributed to 42% (2.5 to 97.5th percentile range 24-59%) of transmissions between 1995-2005, increasing to 64% (37-79%) from 2015-2025. The 10-year PAF of commercial sex is smaller, diminishing from 21% (7-39%) in 1995 to 14% (5-35%) in 2015. Without ART, 49% (32-71%) more HIV infections would have occurred since 2000, when ART was initiated, whereas without condom use since 1985, 67% (27-179%) more HIV infections would have occurred, and the overall HIV prevalence would have been 60% (29-211%) greater than what it is now. Further large decreases in HIV incidence (68%) can be achieved by scaling up ART in MSM to 74% coverage and reducing their susceptibility to HIV by a two-thirds through any prevention modality.ConclusionsUnprote

Journal article

Borquez A, Beletsky L, Nosyk B, Strathdee S, Madrazo A, Abramovitz D, RAfful C, Morales M, Cepeda J, Panagiotoglou D, Krebs E, Vickerman P, Boily MC, Thomson N, Martin Net al., Evaluating the impact of public health oriented drug law reform on HIV incidence among people who inject drugs in Tijuana, Mexico: an epidemic modelling analysis, Lancet, ISSN: 0140-6736

Background: As countries embark on public health-­oriented drug law reform, health impact evaluations are needed. In 2012, Mexico mandated the ‘Narcomenudeo reform’, depenalising possession of small amounts of drugs and instituting drug treatment instead of incarceration. We investigated its impact on HIV incidence among people who iinject drugs (PWID) in Tijuana, Mexico.Methods: We developed a deterministic model of injecting and sexual HIV transmission among PWID in Tijuana disaggregated by sex, incarceration status, syringe confiscation by the police, and exposure to drug treatment/”rehabilitation” (either opioid agonist therapy (OAT) or compulsory drug abstinence programmes (CAP)). We modelled the effect of these exposures on HIV risk among PWID, estimating the impact of observed and potential future reform enforcement levels. Findings: Modelling estimated the limited reform implementation averted 2% [95% Confidence Interval (CI): 0.2-­15 3%] of new HIV infections among PWID between 2012-­2017. If implementation reduced incarceration among PWID by 80% from 2018 onward, 9% [95% CI: 4-­16%] of new HIV infections between 2018-­2030 could be averted, with 21% [95% CI: 10­‐33%] averted if PWID were referred to OAT instead of incarcerated. However, referral to CAP instead of prison could have a lower or potentially negative impact with -­2% [95% CI: 23­‐9%] infections averted. Interpretation Mexican drug law reform has had negligible impact on the HIV epidemic among PWID in Tijuana.

Journal article

Looker K, Ronn M, Brock P, Brisson M, Drolet M, Mayaud P, Boily MCet al., 2018, Evidence of synergistic relationships between HIV and human papillomavirus (HPV): Systematic reviews and meta-analyses of longitudinal studies of HPV acquisition and clearance by HIV status, and of HIV acquisition by HPV status, Journal of the International AIDS Society, Vol: 21, ISSN: 1758-2652

Introduction:Observational studies suggest HIV and human papillomavirus (HPV) infections may have multiple interactions. We reviewed the strength of the evidence for the influence of HIV on HPV acquisition and clearance, and the influence of HPV on HIV acquisition. Methods:We performed meta-analytic systematic reviews of longitudinal studies of HPV incidence and clearance rate by HIV status (review 1) and of HIV incidence by HPV status (review 2). We pooled relative risk (RR) estimates across studies using random-effect models. I2 statistics and subgroup analyses were used to quantify heterogeneity across estimates and explore the influence of participant and study characteristics including study quality. Publication bias was examined quantitatively with funnel plots and subgroup analysis, as well as qualitatively. Results and discussion: Inreview 1, 37 publications (25 independent studies) were included in the meta-analysis. HPV incidence (pooled RR=1.55, 95%CI 1.29-1.88; heterosexual males: pooled RR=1.95, 95%CI 1.62, 2.34; females: pooled RR=1.63, 95%CI 1.26-2.11; men who have sex with men: pooled RR=1.36, 95%CI 1.01-1.82) and high-risk HPV incidence (pooled RR=2.20, 95%CI 1.90-2.54) was approximately doubled among people living with HIV (PLHIV) whereas HPV clearance rate (pooled RR=0.53, 95%CI 0.42-0.67) was approximately halved. Inreview 2, 14 publications (11 independent studies) were included in the meta-analysis. HIV incidence was almost doubled (pooled RR=1.91, 95%CI 1.38-2.65) in the presence of prevalent HPV infection. There was more evidence of publication bias in review 2, and somewhat greater risk of confounding in studies included in review 1. There was some evidence that adjustment for key confounders strengthened the associations for review 2. Misclassification bias by HIV/HPV exposure status could also have biased estimates toward the null. Conclusions:These results provide evidence for synergistic HIV and HPV interactions of clinical and public

Journal article

Wood DT, Kathryn L, Boily MC, Donnell DJ, Cohen M, Kimberley P, Dimiitrov Det al., 2018, Recruitment of female sex workers in HIV prevention trials: can efficacy endpoints be reached more efficiently?, JAIDS-Journal of Acquired Immune Deficiency Syndromes, Vol: 77, Pages: 350-357, ISSN: 1525-4135

Background/Setting: Randomized controlled trials (RCTs) of HIV biomedical prevention interventions often enroll participants with varying levels of HIV exposure, including people never exposed to HIV. We assessed whether enrolling larger proportion of participants with consistently high exposure to HIV, such as female sex workers (FSW), might reduce trial duration and improve the accuracy of product efficacy estimates in future HIV prevention trials. Methods: We used an individual-based stochastic model to simulate event-driven RCTs of an HIV prevention intervention providing 80% reduction in susceptibility per act under different proportions of FSW enrolled. A 5% annual drop-out rate was assumed for both FSW and non-FSW in our main scenario, but rates of up to 50% for FSW were also explored. Results: Enrolling 20% and 50% FSW reduced the median simulated trial duration from 30 months with 0% FSW enrolled to 22 months and 17 months, respectively. Estimated efficacy increased from 71% for RCTs without FSW to 74% and 76% for RCTs with 20% and 50% FSW enrolled, respectively. Increasing the FSW drop-out rate to 50% increased the duration of RCTs by 1-2 months on average and preserved the gain in estimated efficacy. Conclusion: Despite the potential logistical challenges of recruiting and retaining FSW, trialists should revisit the idea of enrolling FSW in settings where HIV incidence among FSW is higher than among non-FSW. Our analysis suggests that enrolling FSW would increase HIV incidence, reduce trial duration and improve efficacy estimates, even if the annual drop-out rate among FSW participants is high.

Journal article

Mitchell KM, Dimitrov D, Hughes J, Xia F, Donnell D, Amico R, Bokock K, CHITWARAKORN A, Bekker L-G, Holtz T, Mannheimer S, Grant R, Boily MCet al., 2018, In what circumstances could non-daily pre-exposure prophylaxis for HIV substantially reduce program costs?, AIDS, Vol: 32, Pages: 809-818, ISSN: 0269-9370

Objectives:To review the main factors influencing the costs of nondaily oral pre-exposure prophylaxis (PrEP) with tenofovir ( emtricitabine). To estimate the costreductions possible with nondaily PrEP compared with daily PrEP for different popula-tions (MSM and heterosexual populations).Design:Systematic review and data triangulation.Methods:We estimated the required number of tablets/person/week for dosing regi-mens used in the HPTN 067/ADAPT (daily/time-driven/event-driven) and IPERGAY (on-demand) trials for different patterns of sexual intercourse. Using trial data, andbehavioural and cost data obtained through systematic literature reviews, we estimatedcost savings resulting from tablet reductions for nondaily versus daily oral PrEP,assuming 100% adherence.Results:Among different populations being prioritized for PrEP, the median reportednumber of days of sexual activity varied between 0 and 2days/week (0–1.5days/weekfor MSM, 1–2days/week for heterosexual populations). With 100% adherence and twoor fewer sex-days/week, HPTN 067/ADAPT nondaily regimens reduced the number oftablets/week by more than 40% compared with daily PrEP. PrEP program costs werereduced the most in settings with high drug costs, for example, by 66–69% with event-driven PrEP for French/US populations reporting on average one sex-day/week.Conclusion:Nondaily oral PrEP could lower costs substantially (>50%) compared withdaily PrEP, particularly in high-income countries. Adherence and efficacy data areneeded to determine cost-effectiveness.

Journal article

Sucharitakul K, Boily MC, Dimitrov D, Mitchell Ket al., 2018, Influence of model assumptions about HIV disease progression after initiating or stopping treatment on estimates of infections and deaths averted by scaling up antiretroviral therapy, PLoS ONE, Vol: 13, ISSN: 1932-6203

BackgroundMany mathematical models have investigated the population-level impact of expanding antiretroviral therapy (ART), using different assumptions about HIV disease progression on ART and among ART dropouts. We evaluated the influence of these assumptions on model projections of the number of infections and deaths prevented by expanded ART.MethodsA new dynamic model of HIV transmission among men who have sex with men (MSM) was developed, which incorporated each of four alternative assumptions about disease progression used in previous models: (A) ART slows disease progression; (B) ART halts disease progression; (C) ART reverses disease progression by increasing CD4 count; (D) ART reverses disease progression, but disease progresses rapidly once treatment is stopped. The model was independently calibrated to HIV prevalence and ART coverage data from the United States under each progression assumption in turn. New HIV infections and HIV-related deaths averted over 10 years were compared for fixed ART coverage increases.ResultsLittle absolute difference (<7 percentage points (pp)) in HIV infections averted over 10 years was seen between progression assumptions for the same increases in ART coverage (varied between 33% and 90%) if ART dropouts reinitiated ART at the same rate as ART-naïve MSM. Larger differences in the predicted fraction of HIV-related deaths averted were observed (up to 15pp). However, if ART dropouts could only reinitiate ART at CD4<200 cells/μl, assumption C predicted substantially larger fractions of HIV infections and deaths averted than other assumptions (up to 20pp and 37pp larger, respectively).ConclusionDifferent disease progression assumptions on and post-ART interruption did not affect the fraction of HIV infections averted with expanded ART, unless ART dropouts only re-initiated ART at low CD4 counts. Different disease progression assumptions had a larger influence on the fraction of HIV-related deaths averted with expande

Journal article

de Montigny S, Boily M, Masse BM, Mitchell KM, Dimitrov Det al., 2018, Assessing the utility of the tipping point ratio to monitor HIV treatment programmes in the era of universal access to ART., Infectious Disease Modelling, Vol: 3, Pages: 85-96, ISSN: 2468-0427

BackgroundThe epidemiological tipping point ratio (TPR) has been suggested as a useful indicator to monitor the scale-up of antiretroviral treatment (ART) programmes and determine when scale-up is sufficient to control the epidemic. TPR has been defined as the ratio of yearly number of new HIV infections to the yearly number of new ART initiations or to the yearly net increase in the number of people on ART. It has been used to rank the progress of treatment programmes across countries, with the objective of reaching a TPR value under 1. Our study aims to assess if TPR alone can be used as an indicator of ART success across settings by comparing the expected changes in HIV incidence and ART coverage when TPR is maintained constant over time. In particular, we focus on the effect of ART initiation timing (emphasis on ART being initiated early or late during HIV progression) on the interpretation of the TPR.MethodsWe used a dynamic model of HIV transmission in South Africa representing ART rollout leading to universal treatment in 2017. The model is calibrated to HIV incidence, HIV prevalence and ART coverage in 2012 in South Africa, and 1000 simulations are selected for the base-case scenario. To measure the effect of TPR, we simulate TPR-preserving interventions, maintaining TPR (yearly number of new ART initiations denominator) at the value observed in 2019 (between 0.65 and 1.25) for 15 years. We compare ART coverage and HIV incidence across TPR values and across strategies in which ART access is prioritized differently. In a secondary analysis, we illustrate the sensitivity of new ART initiations to ART retention, and we compare both definitions of the TPR.ResultsOur analysis shows that HIV incidence reduction is weakly correlated to TPR: the same reduction in HIV incidence (15%) can be achieved by implementing the same strategy with a wide range of TPR maintained (0.65–1.12). Assuming high retention in ART, TPR-preserving strategies prioritizing early ART

Journal article

Tavitian-Exley I, MAHEU-GIROUX M, PLATT L, HEIMER R, UUSKÜLA A, LEVINA O, VICKERMAN P, Boily Met al., 2018, Differences in risk behaviours and HIV status between primaryamphetamines and opioid injectors in Estonia and Russia, International Journal of Drug Policy, Vol: 53, Pages: 96-105, ISSN: 0955-3959

Background and objectivePeople who inject drugs (PWID) account for over half of new HIV infections in Eastern Europe and central Asia, where opioids continue to be the dominant illicit drugs injected. Stimulants including amphetamines (ATS) have been associated with HIV infection risk in several settings. We sought to examine whether primary ATS injection was associated with greater HIV risk, compared to opioid injection in two European locales with significant HIV epidemics.MethodsPWID in Kohtla-Järve and St. Petersburg were recruited using respondent-driven sampling in 2012–2013. Survey data on demographic characteristics, service use, injecting and sexual risk behaviours and HIV-status (and HCV in Kohtla-Järve) were compared between primary opioid and ATS injectors using logistic regression models.ResultsOf 591 injectors recruited in Kohtla-Järve and 811 in St. Petersburg, 195 (33%) and 27 (4%) primarily injected ATS in each city. In both cities, ATS injectors were younger than opioid injectors, initiated injection later, injected less frequently and were more likely to have been paid for sex. In both cities, PWID had high levels of multiple sex partners. In Kohtla-Järve, ATS-injectors had lower odds of back-loading and greater odds of polydrug use than opioid-injectors. In St. Petersburg, where over half of PWID reported unsafe sharing practices, ATS-injectors were less likely to report these practices. ATS-injection was negatively associated with being HIV positive in Kohtla-Järve (aOR = 0.6; 95%CI: 0.5–0.8) and St. Petersburg (aOR = 0.3; 95%CI: 0.1–0.7). ATS-injection was negatively associated with HCV-reactivity in Kohtla-Järve (aOR = 0.5; 95%CI: 0.3–0.6).ConclusionsIn both locations, primary ATS injection was associated with lower injecting risk behaviours, lower odds of HIV and being paid for sex compared to opioid injection. Interventions targeting the characteristics and needs of ATS injectors are need

Journal article

Spicknall I, Looker K, Gottlieb S, Chesson H, Schiffer J, Elmes J, Boily MCet al., Review of mathematical models of HSV-2 vaccination: Implications for vaccine development, Vaccine, ISSN: 0264-410X

Journal article

Wood D, Lancaster K, Boily M, Donnell D, Cohen M, Powers K, Dimitrov Det al., Recruitment of Female Sex Workers in HIV Prevention Trials: Can Efficacy Endpoints Be Reached More Efficiently?, JAIDS-Journal of Acquired Immune Deficiency Syndromes, ISSN: 1525-4135

Journal article

Looker KJ, Elmes JAR, Gottlieb SL, Schiffer JT, Vickerman P, Turner KME, Boily MCet al., 2017, The effect of HSV-2 infection on subsequent HIV acquisition: an updated systematic review and meta-analysis, Lancet Infectious Diseases, Vol: 17, Pages: 1303-1316, ISSN: 1473-3099

Background:HIV and herpes simplex virus type 2 (HSV-2) infections cause a substantial global disease burden and are epidemiologically correlated. Two previous systematic reviews of the association between HSV-2 and HIV found evidence that HSV-2 infection increases the risk of HIV acquisition, but these reviews are now more than a decade old.Methods:For this systematic review and meta-analysis, we searched PubMed, MEDLINE, and Embase (from Jan 1, 2003, to May 25, 2017) to identify studies investigating the risk of HIV acquisition after exposure to HSV-2 infection, either at baseline (prevalent HSV-2 infection) or during follow-up (incident HSV-2 infection). Studies were included if they were a cohort study, controlled trial, or case-control study (including case-control studies nested within a cohort study or clinical trial); if they assessed the effect of pre-existing HSV-2 infection on HIV acquisition; and if they determined the HSV-2 infection status of study participants with a type-specific assay. We calculated pooled random-effect estimates of the association between prevalent or incident HSV-2 infection and HIV seroconversion. We also extended previous investigations through detailed meta-regression and subgroup analyses. In particular, we investigated the effect of sex and risk group (general population vs higher-risk populations) on the relative risk (RR) of HIV acquisition after prevalent or incident HSV-2 infection. Higher-risk populations included female sex workers and their clients, men who have sex with men, serodiscordant couples, and attendees of sexually transmitted infection clinics.Findings:We identified 57 longitudinal studies exploring the association between HSV-2 and HIV. HIV acquisition was almost tripled in the presence of prevalent HSV-2 infection among general populations (adjusted RR 2·7, 95% CI 2·2–3·4; number of estimates [Ne]=22) and was roughly doubled among higher-risk populations (1·7, 1·4&nd

Journal article

Maheu-Giroux M, Vesga JF, Diabate S, Alary M, Baral S, Diouf D, Abo K, Boily M-Cet al., 2017, Changing dynamics of HIV transmission in Cote d'Ivoire: modeling who acquired and transmitted infections and estimating the impact of past HIV interventions (1976-2015), JAIDS-Journal of Acquired Immune Deficiency Syndromes, Vol: 75, Pages: 517-527, ISSN: 1525-4135

Introduction: Understanding the impact of past interventions and how it affected transmission dynamics is key to guiding prevention efforts. We estimated the population-level impact of condom, antiretroviral therapy (ART), and prevention of mother-to-child transmission activities on HIV transmission and the contribution of key risk factors on HIV acquisition and transmission.Methods: An age-stratified dynamical model of sexual and vertical HIV transmission among the general population, female sex workers (FSW), and men who have sex with men was calibrated to detailed prevalence and intervention data. We estimated the fraction of HIV infections averted by the interventions, and the fraction of incident infections acquired and transmitted by different populations over successive 10-year periods (1976–2015).Results: Overall, condom use averted 61% (95% credible intervals: 56%–66%) of all adult infections during 1987–2015 mainly because of increased use by FSW (46% of infections averted). In comparison, ART prevented 15% (10%–19%) of adult infections during 2010–2015. As a result, FSW initially (1976–1985) contributed 95% (91%–97%) of all new infections, declining to 19% (11%–27%) during 2005–2015. Older men and clients mixing with non-FSW are currently the highest contributors to transmission. Men who have sex with men contributed ≤4% transmissions throughout. Young women (15–24 years; excluding FSW) do not transmit more infections than they acquired.Conclusions: Early increases in condom use, mainly by FSW, have substantially reduced HIV transmission. Clients of FSWs and older men have become the main source of transmission, whereas young women remain at increased risk. Strengthening prevention and scaling-up of ART, particularly to FSW and clients of female sex workers, is important.

Journal article

Tavitian-Exley I, Boily MARIE-CLAUDE, Maheu-Giroux M, Heimer R, Uusküla A, Levina Oet al., 2017, Polydrug use and heterogeneity in HIV risk among people who inject drugs in Estonia and Russia: a latent class analysis, AIDS and Behavior, Vol: 22, Pages: 1329-1340, ISSN: 1090-7165

Non-medical drug injection is a major risk factor for HIV infection in Russia and Estonia. Multiple drug use (polydrug) has further been associated with increased harms. We compared HIV, injecting and sexual risk associated with polydrug use among people who injected drugs (PWID) in 2012–2013 in Kohtla-Järve (Estonia, n = 591) and St Petersburg (Russia, n = 811). Using latent class analysis, we identified five (poly)drug classes, the largest consisting of single-drug injectors among whom an opioid was the sole drug injected (56% of PWID). The four remaining polydrug classes included polydrug-polyroute injectors who injected and used opiates and stimulants (9%), opiate-stimulant poly-injectors who injected amphetamine-type-stimulants with a primary opiate (7%) and opiate-opioid poly-injectors who injected opioids and opiates (16%). Non-injection stimulant co-users were injectors who also used non-injection stimulants (12%). In multivariable multinomial regressions, all four polydrug classes were associated with greater injection risks than single-drug injection, while opiate-stimulant and opiate-opioid poly-injection were also associated with having multiple sex partners. Riskier behaviours among polydrug-injectors suggest increased potential for transmission of blood-borne and sexually-transmitted infections. In addition to needles/syringes provision, services tailored to PWID drug and risk profiles, could consider drug-appropriate treatment and sexual risk reduction strategies to curb HIV transmission.

Journal article

Looker KJ, Elmes JAR, Gottlieb SL, Schiffer JT, Vickerman P, Turner KME, Boily M-Cet al., 2017, THE EFFECT OF HSV-2 INFECTION ON SUBSEQUENT HIV ACQUISITION: AN UPDATED SYSTEMATIC REVIEW AND META-ANALYSIS, P3.119 The effect of HSV-2 infection on subsequent hiv acquisition: an updated systematic review and meta-analysis, Publisher: BMJ PUBLISHING GROUP, Pages: A137-A138, ISSN: 1368-4973

Conference paper

Gottlieb SL, Giersing B, Boily M-C, Chesson H, Looker KJ, Schiffer J, Spicknall I, Hutubessy R, Broutet N, WHO HSV Vaccine Impact Modelling Meeting Working Groupet al., 2017, Modelling efforts needed to advance herpes simplex virus (HSV) vaccine development: Key findings from the World Health Organization Consultation on HSV Vaccine Impact Modelling., Vaccine, ISSN: 0264-410X

Development of a vaccine against herpes simplex virus (HSV) is an important goal for global sexual and reproductive health. In order to more precisely define the health and economic burden of HSV infection and the theoretical impact and cost-effectiveness of an HSV vaccine, in 2015 the World Health Organization convened an expert consultation meeting on HSV vaccine impact modelling. The experts reviewed existing model-based estimates and dynamic models of HSV infection to outline critical future modelling needs to inform development of a comprehensive business case and preferred product characteristics for an HSV vaccine. This article summarizes key findings and discussions from the meeting on modelling needs related to HSV burden, costs, and vaccine impact, essential data needs to carry out those models, and important model components and parameters.

Journal article

Maheu-Giroux M, Vesga J, Diabate S, Alary M, Baral S, Diouf D, Abo K, Boily MCet al., 2017, Population-level impact of an accelerated HIV response plan to reach the UNAIDS 90-90-90 target in Côte d’Ivoire: Insights from mathematical modeling, PLoS Medicine, Vol: 14, ISSN: 1549-1277

Background:National responses will need to be markedly accelerated to achieve the ambitious target of the Joint United Nations Programme on HIV/AIDS (UNAIDS). This target aims for 90% of HIV-positive individuals to be aware of their status, for 90% of those aware to receive antiretroviral therapy (ART), and for 90% of those on treatment to have a suppressed viral load by 2020, with each individual target reaching 95% by 2030. We aimed to estimate the impact of various treatment-as-prevention scenarios in Côte d’Ivoire, one of the countries with the highest HIV incidence in West Africa, with unmet HIV prevention and treatment needs, and where key populations are important to the broader HIV epidemic.Methods and findings:An age-stratified dynamic model was developed and calibrated to epidemiological and programmatic data using a Bayesian framework. The model represents sexual and vertical HIV transmission in the general population, female sex workers (FSW), and men who have sex with men (MSM). We estimated the impact of scaling up interventions to reach the UNAIDS targets, as well as the impact of 8 other scenarios, on HIV transmission in adults and children, compared to our baseline scenario that maintains 2015 rates of testing, ART initiation, ART discontinuation, treatment failure, and levels of condom use. In 2015, we estimated that 52% (95% credible intervals: 46%–58%) of HIV-positive individuals were aware of their status, 72% (57%–82%) of those aware were on ART, and 77% (74%–79%) of those on ART were virologically suppressed. Reaching the UNAIDS targets on time would avert 50% (42%–60%) of new HIV infections over 2015–2030 compared to 30% (25%–36%) if the 90-90-90 target is reached in 2025. Attaining the UNAIDS targets in FSW, their clients, and MSM (but not in the rest of the population) would avert a similar fraction of new infections (30%; 21%–39%). A 25-percentage-point drop in condom use from the 2015

Journal article

Maheu-Giroux M, Baral S, Vesga JF, Diouf D, Diabate S, Alary M, Kouame A, Boily MCet al., 2017, Anal intercourse among female sex workers in Côte d’Ivoire: prevalence,determinants, and model-based estimates of the population-level impact onHIV transmission, American Journal of Epidemiology, Vol: 187, Pages: 287-297, ISSN: 1476-6256

urrent evidence suggests that anal intercourse (AI) during sex work is common in sub-Saharan Africa, but few studies investigated the contribution of heterosexual AI to HIV epidemics. Using a respondent-driven sampling survey of female sex workers (FSW) in Abidjan (2014), we estimated AI prevalence and frequency. Poisson regressions were used to identify AI determinants. About 20% of FSW (N = 466) engaged in AI during a normal week (95% confidence intervals: 15-26%). Women who performed AI were generally younger, had been selling sex for longer, were born in Côte d'Ivoire, reported higher sex-work income, more frequent sex in public places, and violence from clients than women not reporting AI. Condom use was lower, condom breakage/slippage more frequent, and use of water-based lubricants was less frequently reported for AI than for vaginal intercourse. Using a dynamic transmission model, we estimated that 22% (95% credible intervals: 11-37%) of new HIV infections could have been averted among FSW during 2000-2015 if AI had been substituted for vaginal intercourse acts. Despite representing a small fraction of all sex acts, AI is an underestimated source of HIV transmission. Increasing availability/uptake of condoms, lubricants, and pre-exposure prophylaxis for women engaging in AI could help mitigate HIV risk.

Journal article

Maheu-Giroux M, Vesga JF, Diabate S, Alary M, Baral S, Boily M, Diouf D, Abo Ket al., 2017, Changing dynamics of HIV transmission in Côte d'Ivoire: modeling which key populations acquired and transmitted infections and estimating the impact of past HIV interventions (1976-2015), JAIDS - Journal of Acquired Immune Deficiency Syndromes, Vol: 75, Pages: 517-527, ISSN: 1525-4135

Introduction: Understanding the impact of past interventions and how it affected transmission dynamics is key to guiding prevention efforts. We estimated the population-level impact of condom, antiretroviral therapy (ART), and prevention of mother-to-child transmission activities on HIV transmission and the contribution of key risk factors on HIV acquisition and transmission. Methods: An age stratified dynamical model of sexual and vertical HIV transmission among the general population, female sex workers (FSW), and men who have sex with men (MSM) was calibrated to detailed prevalence and intervention data. We estimated the fraction of HIV infections averted by the interventions, and the fraction of incident infections acquired and transmitted by different populations over successive 10-year periods (1976-2015). Results: Overall, condom use averted 61% (95% Credible Intervals: 56-66%) of all adult infections during 1987-2015 mainly due to increases by FSW (46% of infections averted). In comparison, ART prevented 15% (10-19%) of adult infections during 2010- 2015. As a result, FSW initially (1976-1985) contributed 95% (91-97%) of all new infections, declining to 19% (11-27%) during 2005-2015. Older men and clients mixing with non-FSW are currently the highest contributor to transmission. MSM contributed ≤4% transmissions throughout. Young women (15-24 years; excluding FSW) do not transmit more infection than they acquired. Conclusion: Early increases in condom use, mainly by FSW, have substantially reduced HIV transmission. Clients of FSW and older men have become the main source of transmission whereas young women remain at increased risk. Strengthening prevention and scaling-up of ART, particularly to FSW and CFSW, is important.

Journal article

Maheu-Giroux M, Tanser F, Boily MC, Pillay D, Joseph SA, Bärnighausen Eet al., 2017, Determinants of time from HIV infection to linkage-to-care in rural KwaZulu-Natal, South Africa, AIDS, Vol: 31, Pages: 1017-1024, ISSN: 0269-9370

Objective: To estimate time from HIV infection to linkage-to-care and its determinants.Linkage-to-care is usually assessed using the date of HIV diagnosis as the startingpoint for exposure time. However, timing of diagnosis is likely endogenous to linkage,leading to bias in linkage estimation.Design: We used longitudinal serosurveys from a large population-based HIV cohort inKwaZulu-Natal (2004-2013) to estimate time of HIV infection. We linked this data topatient records from a public-sector HIV treatment and care program to determine timefrom infection to linkage (defined using the date of the first CD4 count).Methods: We used Cox proportional-hazards models to estimate time from infection tolinkage and the effects of the following covariates on this time: gender, age, education,food security, socio-economic status, area of residence, distance to clinics, knowledgeof HIV status, and whether other household members have initiated ART.Results: We estimated that it would take an average of 4.9 years for 50% ofseroconverters to be linked to care (95% confidence intervals (CI): 4.2-5.7). Among allcohort members that were linked to care, the median CD4 count at linkage was 350cells/μL (95%CI: 330-380). Men and participants <30 years were found to have theslowest rates of linkage-to-care. Time to linkage became shorter over calendar time.Conclusions: Average time from HIV infection to linkage-to-care is long and needs tobe reduced to ensure that HIV treatment-as-prevention policies are effective. Targetedinterventions for men and young individuals have the largest potential to improve linkage rates

Journal article

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