Medical eligibility, comprehension of the consent process, and retention of injection drug users recruited for an HIV vaccine trial

Injection drug users (IDUs) at high risk for human immunodeficiency virus (HIV) infection are being identified as a population for HIV vaccine trials. We studied willingness of drug users to enroll and their comprehension of consent procedures in the context of a Phase II trial at one site. Of 175 people screened for enrollment and whose data sets were complete, 119 (68%) were IDUs. Of the 71 who were eligible, 39 (55%) were IDUs. Exclusion of IDUs was usually for medical reasons. Using a 17-item true/false test, comprehension of the informed consent procedure was high (median score, 16 of 17 for IDUs and non-IDUs); only three subjects (all of whom were IDUs) were excluded from enrollment due to lack of comprehension. Follow-up rates were similar for IDUs and non-IDUs. These data suggest that recruitment of IDUs into HIV vaccine trials is feasible, that IDUs can comprehend and complete the informed consent procedures, and that they return for follow-up visits.