Cognitive factors and willingness to participate in an HIV vaccine trial among HIV-negative injection drug users.

This cross-sectional study involving a cohort of injection drug users (IDU) examined the relationship between cognitive factors (HIV treatment optimism, self-efficacy and knowledge of vaccine trial concepts) as well as risk factors for seroconversion, and willingness to participate (WTP) in a preventive phase 3 HIV vaccine trial. Willingness to participate overall was 56%. In a multivariate analysis, for a 20-unit increase in a 100-point composite scale, self-efficacy was positively related to WTP (adjusted odds ratio [AOR]=1.95, 95% CI=1.40-2.70). HIV treatment optimism and knowledge of vaccine trial concepts were unrelated to WTP. Aboriginal ethnicity (AOR=3.47, 95% CI=1.68-7.18) and a higher educational level (>or=high school) (AOR=1.96, 95% CI=1.07-3.59) were positively related to WTP. This study provides information on WTP for an HIV vaccine trial. Limitations and future directions are also discussed. Copyright (c) 2009 Elsevier Ltd. All rights reserved.