Increased risk behavior among participants in HIV vaccine efficacy trials has been a concern. This study evaluated HIV sexual risk behavior among 5095 HIV-negative men who have sex with men (MSM) and 308 women enrolled in a randomized, double-blind, placebo-controlled efficacy trial of a bivalent rgp120 vaccine at 61 sites, primarily in North America. Sexual risk behavior data were collected at baseline and semiannually for 36 months. Overall, sexual risk behavior did not exceed baseline levels during the trial. Among MSM, younger age (≤30 years), perceived assignment to vaccine, and nonblack race were associated with an increased probability of unprotected anal sex. Among women, unprotected vaginal sex initially decreased but was statistically equivalent to baseline by 24 months, whereas unprotected vaginal sex with HIV-infected partners decreased from baseline, where it remained throughout the trial. HIV sexual risk behavior did not increase among trial participants; however, it was substantial throughout the trial. Consistently high levels of risk behavior and the association of these behaviors to perceived assignment and demographic variables underscore the need for vigilant HIV risk reduction counseling, informed consent, and educational processes in the context of HIV vaccine efficacy trials.
From the *Centers for Disease Control and Prevention, Atlanta, GA; †San Francisco Department of Public Health, San Francisco, CA; ‡University of Washington, Seattle, WA; §New York Blood Center, New York, NY; ∥Ohio State University, Columbus, OH; ¶New York University School of Medicine, New York, NY; #University of Illinois, Chicago, IL; **Fenway Community Health Center, Boston, MA; ††Howard Brown Health Center, Chicago, IL; and ‡‡VaxGen, Inc., Brisbane, CA.
Received for publication January 23, 2004; accepted August 17, 2004.
The primary source of funding for this trial was VaxGen, Inc. Additional funding was provided by the US Centers for Disease Control and Prevention and the US National Institutes of Health.
Reprints: Bradford N. Bartholow, HIV Vaccine Section, Epidemiology Branch, Division of HIV/AIDS Prevention, Center for HIV, STD, and TB Prevention, CDC, 1600 Clifton Road, Mail Stop E-45, Atlanta, GA 30333 (e-mail: firstname.lastname@example.org).