Monday September 10, 2001

HIV Vaccine Subjects Don't Increase Risky Behavior



PHILADELPHIA (Reuters Health) - Despite concerns that participants in AIDS vaccine trials might feel a false sense of security and engage in more risky sexual behaviors, the results of one study show that most such participants actually reduce such behaviors.

At 12 months into the trial, male participants were less likely overall to engage in unprotected anal intercourse, according to a presentation by Dr. Bradford Bartholow of the Centers for Disease Control and Prevention at the AIDS Vaccine 2001 meeting here on Friday.

However, some male trial participants, who believe that they are in the treatment arm of the trial, may be more likely to engage in unprotected anal sex compared with men who believe they are assigned to an inactive placebo or those who are unsure of their assignment.

To investigate, Bartholow's team questioned 5,109 homosexual men and 309 high-risk women enrolled in a placebo-controlled trial currently being conducted at 61 sites, mostly in North America.

Along with HIV risk behavior data gathered at the start of the trial, at 6 months and at 12 months, Bartholow's group assessed the participants' perception of whether they were assigned to the vaccine or the placebo group, along with beliefs about the vaccine's efficacy.

Although the percentage of men reporting unprotected anal intercourse declined from 58% to 50% at 12 months, rates of unprotected anal intercourse were higher among those who thought they had received the vaccine than among the other men.

Among the women, the percentage of unprotected vaginal intercourse decreased from 55% to 39% at 12 months. Their perception about whether they were receiving the vaccine or the placebo did not appear to influence their behavior.

Overall, risk behavior declined in both men and women, Bartholow told Reuters Health. If doctors can address those perceptions associated with risk-taking behavior "through interventions built into a trial, we actually may be able to accelerate the slope of that downward trend even more,'' he said.

For example, if we can identify those men who are more likely to continue high-risk behavior "at the beginning of the trial, we can perhaps triage them into a special education modual.''

The decline in risk-taking behaviors among the female trial participants, many of whom are uneducated commercial sex workers, is also "very encouraging,'' Bartholow said. "The fact that most of them are now using protection is great.''

This is "good news,'' commented Dr. Tim Mastro of the HIV Vaccine Section at the Centers for Disease Control and Prevention. However, Mastro said that "there really is a need to continue education and counseling...and perhaps to design targeted messages for people who somehow perceive that they may be receiving the vaccine and that somehow that may be associated with risk behavior.''