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

229 results found

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

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

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

Boily MC, Shannon K, 2017, Criminal law, sex work, HIV: need for multi-level research, Lancet HIV, Vol: 4, Pages: e98-e99, ISSN: 2405-4704

Journal article

Owen B, Elmes J, Silhol R, Dang Q, McGowan I, Shacklett B, Swann EM, van der Straten A, Baggaley RF, Boily MCet al., 2017, How common and frequent is heterosexual anal intercourse among South Africans? A systematic review and meta-analysis, Journal of International AIDS Society, Vol: 20, ISSN: 1758-2652

Background: HIV is transmitted more effectively during anal intercourse (AI) than vaginal intercourse (VI). However, patterns of heterosexual AI practice and its contribution to South Africa’s generalized epidemic remain unclear. We aimed to determine how common and frequent heterosexual AI is in South Africa.Methods: We searched for studies reporting the proportion practising heterosexual AI (prevalence) and/or the number of AI and unprotected AI (UAI) acts (frequency) in South Africa from 1990 to 2015. Stratified random-effects meta-analysis by subgroups was used to produce pooled estimates and assess the influence of participant and study characteristics on AI prevalence. We also estimated the fraction of all sex acts which were AI or UAI and compared condom use during VI and AI.Results: Of 41 included studies, 31 reported on AI prevalence and 14 on frequency, over various recall periods. AI prevalence was high across different recall periods for sexually active general-risk populations (e.g. lifetime = 18.4% [95%CI:9.4–27.5%], three-month = 20.3% [6.1–34.7%]), but tended to be even higher in higher-risk populations such as STI patients and female sex workers (e.g. lifetime = 23.2% [0.0–47.4%], recall period not stated = 40.1% [36.2–44.0%]). Prevalence was higher in studies using more confidential interview methods. Among general and higher-risk populations, 1.2–40.0% and 0.7–21.0% of all unprotected sex acts were UAI, respectively. AI acts were as likely to be condom protected as vaginal acts.Discussion: Reported heterosexual AI is common but variable among South Africans. Nationally and regionally representative sexual behaviour studies that use standardized recall periods and confidential interview methods, to aid comparison across studies and minimize reporting bias, are needed. Such data could be used to estimate the extent to which AI contributes to South Africa’s HIV epidemic.

Journal article

Brisson M, Benard E, Drolet M, Bogaards JA, Baussano I, Vanska S, Jit M, Boily MC, Smith MA, Berkhof J, Canfell K, Chesson HW, Burger EA, Choi YH, Freiesleben de Blasio B, De Vlas SJ, Guzzetta G, Hontelez JAC, Horn Jet al., 2016, Population-level impact, herd immunity, and eliminationafter human papillomavirus vaccination: a systematicreview and meta-analysis of predictions fromtransmission-dynamic models, Lancet Public Health, Vol: 1, Pages: e8-e17, ISSN: 2468-2667

BackgroundModelling studies have been widely used to inform human papillomavirus (HPV) vaccination policy decisions; however, many models exist and it is not known whether they produce consistent predictions of population-level effectiveness and herd effects. We did a systematic review and meta-analysis of model predictions of the long-term population-level effectiveness of vaccination against HPV 16, 18, 6, and 11 infection in women and men, to examine the variability in predicted herd effects, incremental benefit of vaccinating boys, and potential for HPV-vaccine-type elimination.MethodsWe searched MEDLINE and Embase for transmission-dynamic modelling studies published between Jan 1, 2009, and April 28, 2015, that predicted the population-level impact of vaccination on HPV 6, 11, 16, and 18 infections in high-income countries. We contacted authors to determine whether they were willing to produce new predictions for standardised scenarios. Strategies investigated were girls-only vaccination and girls and boys vaccination at age 12 years. Base-case vaccine characteristics were 100% efficacy and lifetime protection. We did sensitivity analyses by varying vaccination coverage, vaccine efficacy, and duration of protection. For all scenarios we pooled model predictions of relative reductions in HPV prevalence (RRprev) over time after vaccination and summarised results using the median and 10th and 90th percentiles (80% uncertainty intervals [UI]).Findings16 of 19 eligible models from ten high-income countries provided predictions. Under base-case assumptions, 40% vaccination coverage and girls-only vaccination, the RRprev of HPV 16 among women and men was 0·53 (80% UI 0·46–0·68) and 0·36 (0·28–0·61), respectively, after 70 years. With 80% girls-only vaccination coverage, the RRprev of HPV 16 among women and men was 0·93 (0·90–1·00) and 0·83 (0·75–1·00), respectiv

Journal article

Jean K, Boily M-C, Danel C, Moh R, Badje A, Desgrees-du-Lou A, Eholie S, Lert F, Dray-Spira R, Anglaret X, Ouattara Eet al., 2016, What level of risk compensation would offset the preventive effect of early antiretroviral therapy? Simulations from the TEMPRANO trial, American Journal of Epidemiology, Vol: 184, Pages: 755-760, ISSN: 1476-6256

Whether risk compensation could offset the preventive effect of early initiation of antiretroviral therapy (ART) on human immunodeficiency virus (HIV) transmission remains unknown. Using virological and behavioral data collected 12 months after inclusion in the TEMPRANO randomized trial of early ART (Abidjan, Côte d'Ivoire, 2009–2012), we estimated the risk of HIV transmission and compared it between the intervention (early ART; n = 490) and control (deferred ART; n = 467) groups. We then simulated increases in various sexual risk behaviors in the intervention group and estimated the resulting preventive effect. On the basis of reported values of sexual behaviors, we estimated that early ART had an 89% (95% confidence interval: 81, 95) preventive effect on the cumulative risk of HIV transmission over a 1-month period. This preventive effect remained significant for a wide range of parameter combinations and was offset (i.e., nonsignificant) only for dramatic increases in different sexual behaviors simulated simultaneously. For example, when considering a 2-fold increase in serodiscordance and the frequency of sexual intercourse together with a 33% decrease in condom use, the resulting preventive effect was 47% (95% confidence interval: −3, 74). An important reduction of HIV transmission may thus be expected from the scale-up of early ART, even in the context of behavioral change.

Journal article

Menon S, Wusiman A, Boily MC, Kariisa M, Mabeya H, Luchters S, Forland F, Rossi R, Callens S, Vanden Broeck Det al., 2016, Epidemiology of HPV Genotypes among HIV Positive Women in Kenya: A Systematic Review and Meta-Analysis, PLOS One, Vol: 11, ISSN: 1932-6203

BACKGROUND: There is a scarcity of data on the distribution of human papillomavirus (HPV) genotypes in the HIV positive population and in invasive cervical cancer (ICC) in Kenya. This may be different from genotypes found in abnormal cytology. Yet, with the advent of preventive HPV vaccines that target HPV 16 and 18, and the nonavalent vaccine targeting 90% of all ICC cases, such HPV genotype distribution data are indispensable for predicting the impact of vaccination and HPV screening on prevention. Even with a successful vaccination program, vaccinated women will still require screening to detect those who will develop ICC from other High risk (HR) HPV genotypes not prevented by current vaccines. The aim of this review is to report on the prevalence of pHR/HR HPV types and multiple pHR/HR HPV genotypes in Kenya among HIV positive women with normal, abnormal cytology and ICC. METHODS: PUBMED, EMBASE, SCOPUS, and PROQUEST were searched for articles on HPV infection up to August 2nd 2016. Search terms were HIV, HPV, Cervical Cancer, Incidence or Prevalence, and Kenya. RESULTS: The 13 studies included yielded a total of 2116 HIV-infected women, of which 89 had ICC. The overall prevalence of pHR/HR HPV genotypes among HIV-infected women was 64% (95%CI: 50%-77%). There was a borderline significant difference in the prevalence of pHR/HR HPV genotypes between Female Sex workers (FSW) compared to non-FSW in women with both normal and abnormal cytology. Multiple pHR/HR HPV genotypes were highly prominent in both normal cytology/HSIL and ICC. The most prevalent HR HPV genotypes in women with abnormal cytology were HPV 16 with 26%, (95%CI: 23.0%-30.0%) followed by HPV 35 and 52, with 21% (95%CI: 18%-25%) and 18% (95%CI: 15%-21%), respectively. In women with ICC, the most prevalent HPV genotypes were HPV 16 (37%; 95%CI: 28%-47%) and HPV 18 (24%; 95%CI: 16%-33%). CONCLUSION: HPV 16/18 gains prominence as the severity of cervical disease increases, with HPV 16/18 accounting for

Journal article

Mitchell KM, Hoots B, Dimitrov D, Farley J, Gelman M, German D, Flynn C, Adeyeye A, Remien RH, Beyrer C, Paz-Bailey G, Boily M-Cet al., 2016, Potential Impact on HIV Incidence of Increasing Viral Suppression among HIV-positive MSM in Baltimore: Mathematical Modelling for HPTN 078, Conference on HIV Research for Prevention (HIV R4P), Publisher: Mary Ann Liebert, Pages: 64-64, ISSN: 1931-8405

Conference paper

Maheu-Giroux M, Vesga JF, Diabate S, Alary M, Boily M-Cet al., 2016, Modeling the HIV Epidemic in Cote d'Ivoire: Impact of Past Interventions, Conference on HIV Research for Prevention (HIV R4P), Publisher: MARY ANN LIEBERT, INC, Pages: 300-300, ISSN: 0889-2229

Conference paper

Mitchell KM, Prudden HJ, Washington R, Isac S, Rajaram SP, Foss AM, Terris-Prestholt F, Boily MC, Vickerman Pet al., 2016, Potential impact of pre-exposure prophylaxis for female sex workers and men who have sex with men in Bangalore, India: a mathematical modelling study, Journal of the International AIDS Society, Vol: 19, ISSN: 1758-2652

Introduction: In Bangalore, new HIV infections of female sex workers and men who have sex with men continue to occur, despite high condom use. Pre-exposure prophylaxis (PrEP) has high anti-HIV efficacy for men who have sex with men. PrEP demonstration projects are underway amongst Indian female sex workers. We estimated the impact and efficiency of prioritising PrEP to female sex workers and/or men who have sex with men in Bangalore.Methods: A mathematical model of HIV transmission and treatment for female sex workers, clients, men who have sex with men and low-risk groups was parameterised and fitted to Bangalore data. The proportion of transmission attributable (population attributable fraction) to commercial sex and sex between men was calculated. PrEP impact (infections averted, life years gained) and efficiency (life years gained/infections averted per 100 person years on PrEP) were estimated for different levels of PrEP adherence, coverage and prioritisation strategies (female sex workers, high-risk men who have sex with men, both female sex workers and high-risk men who have sex with men, or female sex workers with lower condom use), under current conditions and in a scenario with lower baseline condom use amongst key populations. Results: Population attributable fractions for commercial sex and sex between men have declined over time, and they are predicted to account for 19% of all new infections between 2016 and 2025. PrEP could prevent a substantial proportion of infections amongst female sex workers and men who have sex with men in this setting (23%/27% over 5/10 years, with 60% coverage and 50% adherence), which could avert 2.9%/4.3% of infections over 5/10 years in the whole Bangalore population. Impact and efficiency in the whole population was greater if female sex workers were prioritised. Efficiency increased, but impact decreased, if only female sex workers with lower condom use were given PrEP. Greater impact and efficiency was predicted for the

Journal article

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

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

Journal article

Mishra S, Boily MC, Schwartz S, Beyrer C, Blanchard JF, Moses S, Castor D, Phaswana-Mafuya N, Vickerman P, Drame F, Alary M, Baral SDet al., 2016, Data and methods to characterize the role of sex work and to inform sex work programs in generalized HIV epidemics: evidence to challenge assumptions, Annals of Epidemiology, Vol: 26, Pages: 557-569, ISSN: 1873-2585

In the context of generalized human immunodeficiency virus (HIV) epidemics, there has been limited recent investment in HIV surveillance and prevention programming for key populations including female sex workers. Often implicit in the decision to limit investment in these epidemic settings are assumptions including that commercial sex is not significant to the sustained transmission of HIV, and HIV interventions designed to reach "all segments of society" will reach female sex workers and clients. Emerging empiric and model-based evidence is challenging these assumptions. This article highlights the frameworks and estimates used to characterize the role of sex work in HIV epidemics as well as the relevant empiric data landscape on sex work in generalized HIV epidemics and their strengths and limitations. Traditional approaches to estimate the contribution of sex work to HIV epidemics do not capture the potential for upstream and downstream sexual and vertical HIV transmission. Emerging approaches such as the transmission population attributable fraction from dynamic mathematical models can address this gap. To move forward, the HIV scientific community must begin by replacing assumptions about the epidemiology of generalized HIV epidemics with data and more appropriate methods of estimating the contribution of unprotected sex in the context of sex work.

Journal article

Jean K, Boily MC, Danel C, Moh R, Badge A, Desgrées-du- Loû A, Eholié S, Lert F, Dray-Spira R, Anglaret X, Ouattara Eet al., What Level Of Risk Compensation Would Offset the Preventive Effect of Early ART? Simulations from the Temprano Trial (Abidjan, Côte d’Ivoire), American Journal of Epidemiology, ISSN: 1476-6256

Journal article

Dureau J, Kalogeropoulos K, Vickerman P, Pickles M, Boily M-Cet al., 2016, A Bayesian approach to estimate changes in condom use from limited human immunodeficiency virus prevalence data, Journal of the Royal Statistical Society Series C - Applied Statistics, Vol: 65, Pages: 237-257, ISSN: 0035-9254

Evaluation of large-scale intervention programmes against human immunodeficiency virus (HIV) is becoming increasingly important, but impact estimates frequently hinge on knowledge of changes in behaviour such as the frequency of condom use over time, or other self-reported behaviour changes, for which we generally have limited or potentially biased data. We employ a Bayesian inference methodology that incorporates an HIV transmission dynamics model to estimate condom use time trends from HIV prevalence data. Estimation is implemented via particle Markov chain Monte Carlo methods, applied for the first time in this context. The preliminary choice of the formulation for the time varying parameter reflecting the proportion of condom use is critical in the context studied, because of the very limited amount of condom use and HIV data available. We consider various novel formulations to explore the trajectory of condom use over time, based on diffusion-driven trajectories and smooth sigmoid curves. Numerical simulations indicate that informative results can be obtained regarding the amplitude of the increase in condom use during an intervention, with good levels of sensitivity and specificity performance in effectively detecting changes. The application of this method to a real life problem demonstrates how it can help in evaluating HIV interventions based on a small number of prevalence estimates, and it opens the way to similar applications in different contexts.

Journal article

Lemieux-Mellouki P, Drolet M, Brisson J, Franco EL, Boily M-C, Baussano I, Brisson Met al., 2015, Assortative mixing as a source of bias in epidemiological studies of sexually transmitted infections: the case of smoking and human papillomavirus, Epidemiology and Infection, Vol: 144, Pages: 1490-1499, ISSN: 1469-4409

Journal article

Brisson M, Laprise J-F, Chesson HW, Drolet M, Malagon T, Boily M-C, Markowitz LEet al., 2015, Health and Economic Impact of Switching From a 4-Valent to a 9-Valent HPV Vaccination Program in the United States, Journal of the National Cancer Institute, Vol: 108, ISSN: 0027-8874

Background: Randomized clinical trials have shown the 9-valent human papillomavirus (HPV) vaccine to be highly effective against types 31/33/45/52/58 compared with the 4-valent. Evidence on the added health and economic benefit of the 9-valent is required for policy decisions. We compare population-level effectiveness and cost-effectiveness of 9- and 4-valent HPV vaccination in the United States.Methods: We used a multitype individual-based transmission-dynamic model of HPV infection and disease (anogenital warts and cervical, anogenital, and oropharyngeal cancers), 3% discount rate, and societal perspective. The model was calibrated to sexual behavior and epidemiologic data from the United States. In our base-case, we assumed 95% vaccine-type efficacy, lifelong protection, and a cost/dose of $145 and $158 for the 4- and 9-valent vaccine, respectively. Predictions are presented using the mean (80% uncertainty interval [UI] = 10th−90th percentiles) of simulations.Results: Under base-case assumptions, the 4-valent gender-neutral vaccination program is estimated to cost $5500 (80% UI = 2400–9400) and $7300 (80% UI = 4300−11 000)/quality-adjusted life-year (QALY) gained with and without cross-protection, respectively. Switching to a 9-valent gender-neutral program is estimated to be cost-saving irrespective of cross-protection assumptions. Finally, the incremental cost/QALY gained of switching to a 9-valent gender-neutral program (vs 9-valent girls/4-valent boys) is estimated to be $140 200 (80% UI = 4200−>1 million) and $31 100 (80% UI = 2100−>1 million) with and without cross-protection, respectively. Results are robust to assumptions about HPV natural history, screening methods, duration of protection, and healthcare costs.Conclusions: Switching to a 9-valent gender-neutral HPV vaccination program is likely to be cost-saving if the additional cost/dose of the 9-valent is less than $13. Giving females the 9-valent vaccine provides t

Journal article

Drolet M, Benard E, Boily M-C, Ali H, Baandrup L, Bauer H, Beddows S, Brisson J, Brotherton JML, Cummings T, Donovan B, Fairley CK, Flagg EW, Johnson AM, Kahn JA, Kavanagh K, Kjaer SK, Kliewer EV, Lemieux-Mellouki P, Markowitz L, Mboup A, Mesher D, Niccolai L, Oliphant J, Pollock KG, Soldan K, Sonnenberg P, Tabrizi SN, Tanton C, Brisson Met al., 2015, Population-level impact and herd effects following human papillomavirus vaccination programmes: a systematic review and meta-analysis, LANCET INFECTIOUS DISEASES, Vol: 15, Pages: 565-580, ISSN: 1473-3099

Journal article

Tavitian-Exley I, Vickerman P, Bastos FI, Boily M-Cet al., 2015, Influence of different drugs on HIV risk in people who inject: systematic review and meta-analysis, ADDICTION, Vol: 110, Pages: 572-584, ISSN: 0965-2140

Journal article

Boily M-C, Pickles M, Alary M, Baral S, Blanchard J, Moses S, Vickerman P, Mishra Set al., 2015, What Really Is a Concentrated HIV Epidemic and What Does It Mean for West and Central Africa? Insights From Mathematical Modeling, JAIDS-JOURNAL OF ACQUIRED IMMUNE DEFICIENCY SYNDROMES, Vol: 68, Pages: S74-S82, ISSN: 1525-4135

Journal article

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