Willingness of injection drug users to participate in an HIV vaccine efficacy trial in Bangkok, Thailand

We assessed willingness to participate in an HIV recombinant gp120 bivalent subtypes B/E candidate vaccine efficacy trial among 193 injection drug use rs (IDUs) attending drug treatment clinics in Bangkok;, Thailand. IDUs prev iously enrolled in a prospective cohort study were invited to group session s describing a potential trial, then completed questionnaires assessing com prehension and willingness to participate. A week later, they completed a f ollow-up questionnaire that again assessed comprehension and willingness to participate, as well as barriers to and positive motives for participation , with whom (if anyone) they talked about the information, and whether othe rs thought participation was a good, bad, or neutral idea. At baseline, 51% were definitely willing to participate, and at follow-up 54%; only 3% were not willing to participate at either time. Comprehension was high at basel ine and improved at follow-up. Participants who viewed altruism, regular HI V tests, and family support for participation as important were more willin g to volunteer. Frequency of incarceration and concerns about the length of the trial, possible vaccine-induced accelerated disease progression, and l ack of family support were negatively associated with willingness. Overall, IDUs comprehended the information needed to make a fully informed decision about participating in an rgp120 vaccine efficacy trial and expressed a hi gh level of willingness to participate in such a trial.