A reanalysis of a behavioral intervention to prevent incident HIV infections: including indirect effects in modeling outcomes of Project EXPLORE.

Project EXPLORE - a large-scale, behavioral intervention tested among men who have sex with men (MSM) at-risk for HIV infection - was generally deemed as ineffective in reducing HIV incidence. Using novel and more precise data analytic techniques we reanalyzed Project EXPLORE by including both direct and indirect paths of intervention effects. Data from 4296 HIV-negative MSM who participated in Project EXPLORE, which included 10 sessions of behavioral risk reduction counseling completed from 1999 to 2005, were included in the analysis. We reanalyzed the data to include parameters that estimate the over-time effects of the intervention on unprotected anal (UA) sex and the over-time effects of the intervention on HIV status mediated by UA sex simultaneously in a single model. We found the indirect effect of intervention on HIV infection through UA sex to be statistically significant up through 12-month post-intervention, OR = 0.83, 95% CI = 0.72-0.95. Furthermore, the intervention significantly reduced UA sex up through 18-month post-intervention, OR = 0.79, 95% CI = 0.63-0.99. Our results reveal effects not tested in the original model that offer new insight into the effectiveness of a behavioral intervention for reducing HIV incidence. Project EXPLORE demonstrated that when tested against an evidence-based, effective control condition can result in reductions in rates of HIV acquisition at one year follow-up. Findings highlight the critical role of addressing behavioral risk reduction counseling in HIV prevention.