The HPTN 064 (ISIS Study)—HIV Incidence in Women at Risk for HIV: US
Sally Hodder*1, J Justman2, J Hughes3, J Wang3, D Haley4, A Adimora5, C Del Rio6, L Soto-Torres7, S Eshleman8, W El-Sadr2, and HIV Prevention Trials Network (HPTN) 064 Study Team
1Univ of Med and Dentistry of New Jersey, Newark, US; 2Columbia Univ, Mailman Sch of Publ Hlth, New York, NY, US; 3Fred Hutchinson Cancer Res Ctr, Seattle, WA, US; 4FHI 360, Durham, NC, US; 5Univ of North Carolina at Chapel Hill Sch of Med, US; 6Emory Univ, Rollins Sch of Publ Hlth and Ctr for AIDS Res, Atlanta, GA, US; 7NIAID, NIH, Bethesda, MD, US; and 8Johns Hopkins Univ Sch of Med, Baltimore, MD, US
Background: Approximately 25% of HIV infections in the US occur in women, 67% of whom are black. Despite these numbers, past efforts have failed to identify populations of US women with sufficient HIV incidence to enable conduct of HIV prevention trials with an HIV incidence endpoint.
Methods: An innovative approach was used to recruit US women at risk for HIV infection. This involved detailed ethnographic mapping of venues frequented by at-risk women within communities defined by high HIV prevalence and poverty rates. Within those venues, women without a prior HIV diagnosis (by self-report) and with ≥1 individual or partner risk characteristic were recruited using venue-based sampling from 6 US communities. Enrolled women were followed for 6 to 12 months with HIV testing, and Audio Computer-Assisted Self Interviews (ACASI) were conducted at each visit. Testing for acute infection was performed retrospectively. Longitudinal incidence was calculated (as events/person-years). Cross-sectional incidence was calculated using methods of McWalter and Welke (2010). Confidence intervals (CI) were calculated on the log scale and back-transformed. A randomization test was used to compare incidence rates between time periods.
Results: We enrolled 2099 women (88% black, 8% white, 12% Hispanic). Characteristics and risk behaviors are shown in the table: 32 women (1.5%) were newly diagnosed as HIV+ at enrollment (baseline); 2 additional women had acute infection at baseline (estimated annual incidence 2.52%, 95%CI 0.60 to 10.7); 4 women acquired HIV during follow-up (estimated annual incidence 0.24%, 95%CI 0.09 to 0.65). The annual incidence estimate based on acute infection at enrollment was significantly higher than the annual incidence estimate based on seroconversion (p = 0.027).
Conclusions: Recruitment from geographic “hotspots” of HIV infection identified a cohort of US women with few partners, but prevalent risk behaviors: 32 women were newly diagnosed at enrollment and 2 more had acute HIV infection at enrollment. HIV incidence in HPTN 064 (ISIS) was substantially (5 times) higher than CDC 2009 annual HIV incidence estimate for US black women (0.05%) and comparable to estimated HIV adult incidence rates in parts of sub-Saharan Africa (Congo 0.28% and Kenya 0.53%), underscoring the urgency of conducting prevention trials among women at risk for HIV infection in the US.