EXPLORE: A Randomized Clinical Trial of the Efficacy of a Behavioral Intervention to Prevent Acquisition of HIV among Men who have Sex with Men (MSM)

Study Summary

What was HIVNET 015 (EXPLORE)?

HIVNET 015 was the first study to test a behavioral intervention specifically for men who have sex with men (MSM) over an extended period of time using HIV infection as the primary endpoint.

Who participated in the study?

4,295 HIV-negative MSM were enrolled in six U.S. cities: Boston, Chicago, Denver, New York, San Francisco and Seattle

What happened during the study?

Following enrollment, study participants in the standard treatment arm underwent HIV testing, received HIV-prevention counseling and completed extensive questionnaires regarding sexual behaviors, alcohol and drug use, and occurrence of sexually transmitted diseases every six months. Study participants in the intervention treatment arm completed the same activities as those in the standard arm, but they received additional counseling in the form of multiple intensive behavioral counseling sessions (with motivational interviewing and cognitive behavior theory, for example, as key components) during the first three to four months of their study involvement period. Afterward, participants received "booster" sessions every three months (for up to, on average, 3.25 years).

Why was this study important?

Many research studies had been conducted involving populations of MSM to identify interventions which can help MSM to reduce the frequency of sexual behaviors that put them at risk of getting HIV. Extensive changes in risk behaviors had occurred among MSM but, in recent years at the time of the study, HIV infections, other sexually transmitted diseases and sexual risk behaviors had been increasing, emphasizing the critical need for identifying effective prevention interventions. EXPLORE examined the potential of one such intervention to reduce HIV infection rates among MSM.


The individual factors examined were associated with sexual risk behavior. The cohort was shown to be heterogeneous in regard to the presence of combinations of these risk-related factors.

Study Documents

Study Details

Protocol Status: Concluded
Study Purpose:

To determine the efficacy of a behavioral intervention to prevent acquisition of HIV among men who have sex with men.

Study Design:

The study is a two-armed, multi-site, prospective randomized controlled Phase IIB “screening” trial of 4,350 MSM, who are HIV antibody negative, and who report engaging in anal sex within the 12 months prior to enrollment. There will be a 1:1 random assignment of participants to receive either the behavioral intervention or the control risk reduction counseling. Participants will be recruited from six domestic HIVNET study sites that currently have cohorts of MSM.

Study Population:

Sexually active MSM, i.e., those who report engaging in anal sex within the 12 months prior to enrollment who are HIV antibody negative are eligible to participate.

Study Size:

4295 MSM

Study Duration:

4.5 years (from 2/99 through 7/03).

Treatment Regimen:

This is a behavioral intervention study.

Primary Objectives:

To evaluate the efficacy of a behavioral intervention to reduce seroincidence of HIV infections in a population of MSM.

Secondary Objectives:

To evaluate the efficacy of a behavioral intervention to prevent acquisition of HSV-2 and rectal and urethral gonorrhea.
To assess self-reported behavior change as a correlate of protection against acquisition of HIV, HSV-2 , and GC infections.
To assess the effect of the intervention track targeting alcohol and other drug use on sexual risk-taking associated with alcohol and other drug use.
To evaluate the cost and cost-effectiveness of the intervention in averting HIV infections and in averting HSV-2 and gonorrhea infections).

Study Sites List