Background Clinical trial protocol adherence and retention are often considered challenges that are especially difficult to achieve among certain high-risk populations. The HIV infection rate among heterosexual African-American women is increasing, making their participation in clinical trials of HIV behavioural and biomedical prevention interventions more important. We identify drug use and sex risk factors associated with adherence to protocol and study retention among this population during the course of an HIV vaccine trial.
Methods Data from participants at the Philadelphia, PA site for the HIV Vaccine Trials Network (HVTN) 502 study testing the Merck Adenovirus 5 gag-pol-nef HIV vaccine were used to examine factors associated with adherence (receipt of three vaccines) and retention (present for 12-month appointment). Enrollees included 123 HIV-negative women 18–45 years of age reporting regular use of crack cocaine and frequent unprotected sex, who were randomly assigned to receive three injections of either the study vaccine or a placebo vaccine.
Results Study participants had a mean age of 37 years and 91% were African–American. Overall adherence to study protocol was 89% and study retention at one year was 93.5%. Analyses found no association between drug use and high-risk sex behaviours and poorer rates of adherence and retention. In fact, participants who used recreational drugs at baseline were more likely than those who did not to adhere to study protocol (92% vs 75%, p<0.10). Participants who reported use of injectable contraceptives at baseline were less likely than those who did not to be retained in the study at 1 year (57% vs 96%, p<0.01). Other measures of drug use (whether injected recreational drugs, and used crack cocaine, speed and other drugs) and sex risk (whether had a STI, exchanged vaginal, oral or anal sex for money, drugs or services, used different methods of birth control, the number of male sex partners, whether aware of partner's HIV status and whether had protective and unprotected vaginal, anal or oral sex with them) were not associated with adherence and retention.
Conclusions Factors commonly assumed to interfere with trial participation were not associated with adherence to study protocol or retention. These findings suggest that drug use and sexual risk behaviours do not impede completion of vaccinations and protocol required visits in clinical trials of experimental HIV vaccines.
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