PrEP Did Not Increase Sexual Risks in Study of Gay Men

According to a recent trial, pre-exposure prophylaxis (PrEP) did not cause men who have sex with men (MSM) to have riskier sex, said researchers, although they warned that the subjects may not have been completely honest in their self-reporting of the sexual risks they took.

"There was no evidence of risk compensation among HIV-uninfected MSM in this clinical trial," reads the study conclusion. "Monitoring for risk compensation should continue now that pre-exposure prophylaxis has been shown to be efficacious in MSM and other populations and will be provided in open-label trials and other contexts."

Publishing their findings in the Journal of Acquired Immune Deficiency Syndromes, researchers conducted a randomized, double-blind, placebo-controlled trial of Viread (tenofovir) as PrEP with 400 HIV-negative MSM in San Francisco, Atlanta and Boston who had reported anal sex with another man in the past year.

In PrEP, HIV-negative people who are at a high risk for HIV take a daily HIV antiretroviral or combination ARV pill to lower the risk of transmission. But researchers were concerned that taking PrEP might lead their patients to a phenomenon known as risk compensation: If people taking the therapy consider themselves more invincible to infection, they might take more sexual risks.

Researchers divided study participants into four random, even groups and have them either Viread or a placebo. They either started the drug immediately, or after a delay of nine months. Both groups then continued to take it for 24 months. Doctors then assessed the subjects' risk factors at the beginning of the study, and every three months, at follow-up interviews.

Doctors found that the men's risk factors either dropped or stayed at the same level, with the average number of sexual partners and unprotected anal intercourse falling or not changing significantly. This level of risk factor remained the same when half the group was delayed in taking the drugs, or when both groups were taking either the therapy or placebo.

According to the original data, the participants had an average of 7.25 partners in the three months prior to the study. This number decreased to 6 partners between months 3 and 9 and to 5.71 in the second year.

Before baseline, 57 percent of participants reported unprotected anal sex. The number dropped to 48 percent between months 3 and 9, and rose to 52 percent in the second year. Also, at baseline, 29 percent of participants reported unprotected intercourse with a man they knew to be HIV-positive. This number dropped to 21 percent between months 3 and 9 and increased slightly to 22 percent in the second year.

Unprotected sex with partners they knew to be HIV-positive decreased from 2 at the beginning of the study to 1.37 during the second year, and unprotected anal intercourse with partners believed to be HIV-negative increased from 2.75 at baseline to 4 during year two.

For all intents and purposes, the study seems to indicate that those subjects who took PrEP actually increased their safer sex protocols during their participation in the Truvada trial.

But the study has some limitations, primarily that participants were told that PrEP had no known efficacy. Their willingness to take risks therefore might not be equal to a real-world situation. Also, doctors warn that self-reporting of sexual risks may not be reliable, as subjects may have depicted their behavior as less risky than it actually was.