CROI 2019 Abstract eBook

Abstract eBook

Poster Abstracts

substantially reduce HIV incidence among ANC patients, their partners, and their infants. Methods: We constructed a mathematical model describing horizontal and vertical HIV transmission during pregnancy within patient-partner and patient-infant dyads, respectively. We based biological and behavioral inputs on literature estimates and ANC program data fromMalawi and Zambia. We modeled three main HIV prevention strategies, alone and in combination, by varying: 1) male partner HIV testing from a base-case value of 15% to a target of 35%; 2) suppressive antiretroviral therapy (ART) for HIV-positive ANC patients and partners from a base-case of 70% to a target of 90%; and 3) adherent pre-exposure prophylaxis (PrEP) use for HIV-uninfected female ANC patients from a base-case of 0% to a target of 20%. Using the model, we estimated the percentage of horizontal and vertical HIV infections that could be averted with these strategies, relative to the current (base-case) scenario. Results: Increasing male partner testing to 35% coverage was predicted to reduce horizontal and vertical transmissions by 16.7% and 15.1%, respectively (scenario 2, Table); corresponding reductions with 20% female PrEP use were 13.4% and 12.1% (scenario 4). Jointly increasing coverage of both interventions by 20 percentage points was predicted to reduce horizontal and vertical transmissions by ~one-quarter (scenario 7); this reduction increased to ~one-third with a combination of these two interventions plus increasing suppressive ART (scenario 8). Across scenarios, a 20-percentage-point increase in suppressive ART for HIV-positive patients and partners had only a modest incremental impact (scenarios 3 vs. 1, 5 vs. 2, 6 vs. 4, 8 vs. 7). Conclusion: Our modeling suggests that combination HIV prevention in ANC settings – particularly approaches that increase male partner testing and female PrEP use – could substantially reduce HIV incidence among pregnant women, their partners, and their newborns in sub-Saharan Africa. 1087 SCALE-UP OF ART AND VMMC EXPLAIN A TWO-FOLD DECLINE IN HIV INCIDENCE IN WESTERN KENYA Anna Bershteyn 1 , Adam N. Akullian 1 , Daniel J. Klein 1 , Britta Jewell 2 , Kennedy Mutai 3 , Samuel M. Mwalili 4 1 Institute for Disease Modeling, Bellevue, WA, USA, 2 University of California San Francisco, San Francisco, CA, USA, 3 National AIDS Control Council, Nairobi, Kenya, 4 CDC, Nairobi, Kenya Background: Western Kenya has among the world’s highest prevalence of HIV, with one in four adults infected in Siaya and Homa Bay Counties. Longitudinal surveillance of a community in Siaya found that incidence has fallen by two-fold between 2011 and 2016. We used mathematical modeling to estimate the relative contribution of antiretroviral therapy (ART) and voluntary male medical circumcision (VMMC) to the declines in HIV incidence in the Western Kenya region, including the county of Siaya. Methods: EMOD-HIV, an individual-based HIV transmission and care continuummodel, was used to simulate the HIV pandemic in Western Kenya. The model was calibrated to age-, sex-, and county-specific HIV prevalence estimates from four national surveys, as well as estimates of population size and structure, number on ART, number receiving VMMC, and national targets for VMMC coverage. Conservatively, we assumed a sustained ART coverage of approximately 60%. Calibration yielded 250 best-fitting model trajectories for each of six counties comprising the Nyanza region of Western Kenya. In Siaya County, EMOD-HIV recapitulated the halving of HIV incidence over 2011-2016 at the county level, despite the model fitting process not directly utilizing incidence estimates from the longitudinal surveillance site in this county. The baseline model trajectories were modified to simulate what would have happened in the absence of ART and/or VMMC. Results: Estimated HIV incidence declined drastically in Siaya due to scale-up of ART and VMMC, without which incidence would have remained stable at

1.7 new infections per 100 person-years among adults age 15-49 (Figure 1). Incidence peaked in 2002, fell to half of its peak by 2018, and continued to decline to one-third of peak levels by 2028. ART is the predominant cause of incidence declines up until 2025, after which VMMC is expected to surpass ART as a driver of incidence decline, provided Siaya achieves and maintains a target of 80% VMMC coverage. Similar trends were found in other high-prevalence counties in Western Kenya. Conclusion: Epidemiological modeling suggests that observed incidence declines in Siaya County, Western Kenya, can be fully attributed to scale-up of ART and VMMC, without which incidence would have remained stable. Incidence is expected to continue to decline due to these interventions, but enhanced efforts to prevent HIV infections will be required to accelerate declines and bring incidence to low levels.

Poster Abstracts

1088 SIMULATED VACCINE EFFICACY TRIALS TO ESTIMATE HIV INCIDENCE IN KEY POPULATIONS AndrewM. Abaasa 1 , Stephen Nash 1 , Yunia Mayanja 2 , Matt A. Price 3 , Patricia E. Fast 3 , Pontiano Kaleebu 2 , Anatoli Kamali 3 , Jim Todd 1 1 London School of Hygiene & Tropical Medicine, London, UK, 2 MRC/UVRI and LSHTM Uganda Research Unit, Entebbe, Uganda, 3 International AIDS Vaccine Initiative, New York, NY, USA Background: Fisherfolks (FF) on Lake Victoria shoreline and female sex workers (FSW) in Kampala, Uganda could be suitable key populations for HIV vaccine efficacy trials because of the high HIV incidence and good retention in observational cohorts. However, HIV incidence may vary from observational cohorts, once volunteers have enrolled into a trial. We used simulated vaccine efficacy trials (SiVET) nested within observational cohorts in these populations to evaluate this question. Methods: SiVETs were nested in two observational cohorts, in FF (Jul 2012-Apr 2014) and FSW (Aug 2014-Apr 2017). When observational cohort participants presented for quarterly visits (3-18 months) they were consecutively screened for enrolment into SiVET. Eligibility was: age 18-49 years, HIV negative; at high risk of HIV infection; no history of severe allergic reaction to any substance. Those not enrolled continued participation in the observational cohort. In addition to procedures (HIV testing & risk assessment) in the observational cohorts, SiVET participants were given a licensed Hepatitis B vaccine following a standard schedule of 0, 1 and 6 months, mimicking a schedule of an HIV vaccine efficacy trial. HIV testing was carried out quarterly for one year. Results: In total, 3989 participants were enrolled into the observational cohorts. Of these 3622 (90.8%) returned at least once and 1525 (42.1%) were eligible for SiVET screening: 672 (44.1%) were screened and 572 (282 FF and 290 FSW) enrolled. HIV incidence in the observational cohorts pre SIVET was 4.5/100 person years at risk (PYAR), 95%CI: 3.8-5.5 [FF=4.9 (3.9-6.2); FSW=4.0 (2.9- 5.5)]. When a subset of participants was enrolled into SiVETs, the HIV incidence at 12 months was lower in SiVETs, 3.5/100 PYAR, 95%CI: 2.2-5.6 [FF=3.8 (2.7-7.1); FSW=3.2 (1.5-6.6)] compared to 5.9/100 PYAR, 95%CI: 4.3-8.1[FF=8.3 (5.6-12.4); FSW=4.1 (2.5-6.7)] in the observational cohorts’ concurrent period, p=0.034. Compared to observational cohorts, SiVETs recruited more men, older

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