Background: Assess the possible acceptability of oral chemoprophylaxis as a strategy for preventing HIV infection among persons at high risk for non-occupational exposure to HIV.

Methods: Self-administered questionnaire completed by 4,572 HIV-seronegative study participants (94% of enrollees) at the Month 6 follow-up visit (11/95-5/96) of a prospective cohort study in 8 US cities.

Results: Gay/bisexual men (n=3,095) were twice as likely to favor a preventive HIV vaccine over oral chemoprophylaxis, while other at risk populations (694 men and 466 women injection drug users [IDUs], and 317 women at heterosexual risk) preferred oral chemoprophylaxis (p<0.001). Compared to white gay/bisexual men, black gay/bisexual men were less than half as likely to favor vaccines (O.R.=0.43, C.I., 0.32, 0.59). Asked "how willing would you be to help test a medication that might protect people from HIV infection if you had to take a pill every day?" as part of a randomized, placebo-controlled trial, attitudes varied by risk group (p=0.02 for the comparison definitely/probably not willing versus definitely/ probably willing): gay/bisexual men and male IDUs were more willing (71% and 70% respectively), than women IDUs (68%) and women at heterosexual risk (64%). When a continuous dosing regimen involved three doses per day and included side effects, only 30% of participants said they would be willing to participate. Gay/bisexual men at greater risk (unprotected receptive anal sex with multiple partners of HIV+ or unknown status partners) were more likely to be willing to join a study of a "morning after pill" than other gay/bisexual men (p=0.006). Within other populations, there were no associations between reported sexual or injection-related risk behaviors and willingness to enroll.

Conclusions: Prior to broad public discussion of post-exposure prophylaxis for sexual exposures, this high risk HIV-seronegative cohort evinced little enthusiasm for continuous use of drugs that require 3X/day dosing and elicit side effects. The association between increased HIV risk behavior and greater willingness to participate suggests that studies of this approach must include thorough counseling about its uncertain effectiveness.

Michael Gross
Abt Associates Inc.
4800 Montgomery Lane
Bethesda, MD 20814