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

There are gaps in our knowledge of the role cognitive factors play in determining people's willingness to participate (WTP) in therapeutic HIV vaccine trials. Using a cross-sectional study of HIV-positive injection drug users (IDU), we determined the role of three cognitive factors: HIV treatment optimism, self-efficacy beliefs, and knowledge of vaccine trial concepts in relation to WTP in a hypothetical phase 3 therapeutic HIV vaccine trial. WTP was 54%. Participants tended to be low in HIV treatment optimism (mean = 3.9/10), high in self-efficacy (mean = 79.8/100), and low in knowledge (mean = 4.1/10). Items pertaining to HIV treatment optimism and knowledge of HIV vaccine trial concepts were generally unrelated to WTP. An increase in self-efficacy had a statistically significant positive association with WTP (OR = 1.61, 95% CI = 1.04-2.46, p < 0.05). Furthermore, most of these HIV-positive participants had high levels of self-efficacy, so we are most confident about this relationship at such levels. These findings indicate that interventions focused on increasing self-efficacy could enhance WTP among HIV-positive IDU.