CROI 2018 Abstract eBook

Abstract eBook

Oral Abstracts

We assumed HIV-negative participants were at-risk during the entire period between cycles. Participants who tested positive for HIV infection at their first NHBS interview were excluded. We calculated person-years at risk from the individual time between cycles and used the total number of seroconversions to estimate incidence and a binomial distribution to approximate variance. Results: Successive surveys recaptured nested cohorts of 1,110 MSM, contributing 5080 person-years, 2,548 PWID, contributing 12,283 person- years and 855 heterosexuals at high risk, contributing 3,941 person-years. We observed 127 seroconversions or an incidence rate of 2.5 per 100 person-years (95% confidence interval [CI]: 2.1 to 3.0 per 100 person-years) among MSM; 73 seroconversions or an incidence rate of 0.6 per 100 person-years (95% CI: 0.5 to 0.7 per 100 person-years) among PWID; 17 seroconversions or an incidence rate of 0.4 per 100 person-years (95% CI: 0.2-0.6 per 100 person-years) among HET. Conclusion: These estimates are consistent with previously published incidence estimates among these populations. Measuring incidence can be challenging. Using repeat cross-sectional surveys to simulate a cohort, may serve as another strategy in estimating HIV incidence. 45 FEMALE HIV ACQUISITION PER SEX ACT IS ELEVATED IN LATE PREGNANCY AND POSTPARTUM Kerry A. Thomson 1 , James P. Hughes 1 , Jared Baeten 1 , Grace John-Stewart 1 , Connie L. Celum 1 , Craig R. Cohen 2 , Nelly R. Mugo 1 , James Kiarie 1 , Renee Heffron 1 1 University of Washington, Seattle, WA, USA, 2 University of California San Francisco, San Francisco, CA, USA Background: In many settings with high HIV prevalence, fertility rates are also high and women spend a significant proportion of their reproductive years pregnant, postpartum, or breastfeeding. Some, but not all, studies have demonstrated significantly higher HIV incidence during pregnancy. Per sex act analyses contribute an understanding of the absolute and relative risks of HIV transmission, and can provide insight into whether increased risk during pregnancy and postpartum is attributable to biological or sexual behavior changes. These data are critical to inform the delivery of HIV prevention interventions for women. Methods: 2,751 African HIV serodiscordant couples with HIV uninfected female partners were followed prospectively for ≤48 months in two HIV prevention studies. Sexual frequency and condom use was reported monthly. HIV and pregnancy testing occurred monthly or quarterly depending on the study. Study time was categorized by reproductive stage as early pregnancy, late pregnancy, up to 6 months postpartum, or non-pregnant. HIV events that could not be linked between study partners by genetic sequencing were excluded. We used a complementary log-log model to compare the probability of male-to-female HIV transmission per sex act by reproductive stage. The reference case for HIV transmission probability is a condomless sex act between a 25 year old woman not using PrEP and a male partner with HIV RNA of 10,000 copies/ml. Results: Pregnancy incidence was 12.50 per 100 woman-years (95% CI: 11.52-13.55) and 82 HIV transmission events occurred. The HIV transmission probability was 1.05 per 1,000 sex acts when women were not pregnant, 2.19 in early pregnancy, 2.97 in late pregnancy, and 4.18 in postpartumwomen (Figure). After adjustment for condom use, age, use of PrEP, and HIV viral load, the probability of HIV transmission per sex act was significantly higher in late pregnancy (aRR 2.82, p=0.01) and postpartum (aRR 3.97, p=0.01) compared to non-pregnant time. Conclusion: The risk of HIV transmission per sex act steadily increased through pregnancy and was highest during postpartum, even after accounting for sexual behavior, PrEP, and HIV viral load, suggesting that biological changes during these periods increase HIV risk. While further research is needed to better understand biological susceptibility, scale-up of HIV prevention and testing in antenatal and postpartum care in high HIV prevalence settings is warranted to prevent sexual transmission and identify acute maternal HIV infections.

Oral Abstracts

46 SHARP DECLINE IN MALE HIV INCIDENCE IN A RURAL SOUTH AFRICAN POPULATION (2004–2015) Alain Vandormael 1 , Adam N. Akullian 2 , Adrian Dobra 2 , Tulio de Oliveira 3 , Frank Tanser 1 1 Africa Health Research Institute, Mtubatuba, South Africa, 2 University of Washington, Seattle, WA, USA, 3 University of KwaZulu-Natal, Durban, South Africa Background: The extraordinary scale-up of antiretroviral therapy (ART) is expected to reduce the rate of new HIV infections at the population level. In this study, we calculated the incidence of HIV for males and females using data from a complete South African population. Methods: The Africa Health Research Institute (AHRI) maintains an annual HIV surveillance system in the Umkhanyakude district of the KwaZulu-Natal province. Between 2004 and 2015, we followed 6,287 males (aged 15–54 years) and 8,661 females (aged 15–49 years) from their earliest HIV-negative test date until their latest HIV-negative or earliest HIV-positive test date. In addition, we obtained viral load measurements from all HIV-positive participants in 2011, 2012, and 2014 and included ART initiation data from the 17 health-care clinics in the AHRI surveillance area. Results: The HIV incidence rate declined among males aged 15–25 years between 2012 and 2015, from 1.70 (95% CI: 1.13–2.26) to 0.60 (95% CI: 0.00– 1.29) events/100 person-years, as well as for males aged 25–54 years, from 3.28 (95% CI: 1.97–4.55) to 1.87 (95% CI: 0.60–3.56) events/100 person-years. For females aged 15–25 years, however, the HIV incidence rate increased from 6.32 (95% CI: 5.34–7.32) to 6.67 (95% CI: 5.25–8.16) events/100 person-years between 2013 and 2015. Throughout the study period, the HIV incidence rate was flat for females aged 25–49 years, ranging from 4.14 (95% CI: 3.35–5.01) to 5.00 (95% CI: 4.37–5.69) events/100 person-years. ART coverage was significantly higher in woman, increasing from 28.3% to 43.6% between 2010 and 2013, when compared with men, which increased from 26.7% to 32.3%. Among woman aged 15–25 years, the virologic suppression level increased from 20.8% (95% CI: 16.5–25.2%) in 2011 to 40% (95% CI: 34.4-45.7%) in 2014. During this period, the virologic suppression level increased only slightly for men of the same age group, from 15.2% (95% CI: 5.8–24.7%) to 18.5% (95% CI: 7.8–29.2%). Conclusion: The HIV incidence rate declined for all men aged 15–54 years between 2012 and 2015 but increased among young woman aged 15–25 years. We hypothesize that the more conscientious treatment-and-care behaviors of woman-i.e., higher ART uptake and higher rates of virologic suppression-has begun to protect men from acquiring HIV.

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CROI 2018