Behavioral interventions reduce self-reported unprotected anal sex among MSM. These results indicate that HIV prevention for this population can work and should be supported. 
Results of previous studies provide a benchmark for expectations in new studies. Meta-analysis can inform future design and implementation in terms of sample size, target populations, settings, goals for process measures, and intervention content.
When effects differ by design variables, which are deliberately selected and planned, awareness of these characteristics may be beneficial to future designs. Researchers designing future small group and individual-level studies should keep in mind that to date, effects of the greatest magnitude have been observed in studies that used count outcomes and a shorter intervention span (up to 1 month).
Among small group and individual-level studies, effects were also greatest when the comparison condition included minimal to no HIV prevention content. Nevertheless, statistically significant favorable effects were also seen when the comparison condition included standard or other HIV prevention content. Researchers choosing the latter option for new studies should plan for larger sample sizes based on the smaller expected net intervention effect noted above.
When effects differ by implementation variables, which become evident as the study is conducted but are not usually selected or planned, caution may be advised so that future studies can reduce bias. Because intervention effects were somewhat stronger (though not statistically significantly so) in studies with a greater attrition in the comparison condition, differential retention may be a threat to validity. Extra effort should be given to retaining participants in comparison conditions.
Among community-level interventions, intervention effects were strongest among studies with random assignment of groups or communities. Therefore the inclusion of studies where assignment of groups or communities was by convenience did not exaggerate the summary effect. The greater effectiveness of interventions including more than 25% non-gay identifying MSM suggests that when they can be reached, these men may be more responsive than gay-identified men to risk reduction efforts. Non-gay identified MSM may have had less exposure to previous prevention messages, so their initial exposure may have a greater impact.
The greater effectiveness of interventions that include efforts to promote personal skills such as keeping condoms available and behavioral self-management indicates that such content merits strong consideration in development and delivery of new interventions for MSM. And the finding that interventions were most effective for majority white populations underscores the critical need for effective interventions for MSM of African and Latino descent.
Further research measuring the incidence of HIV and other STDs is needed. Because most studies were conducted among mostly white men in the US and Europe, more evaluations of interventions are needed for African American and Hispanic MSM as well as MSM in the developing world. More research is also needed to further clarify which behavioral strategies (e.g., reducing unprotected anal sex, having oral sex instead of anal sex, reducing number of partners, avoiding serodiscordant partners, strategic positioning, or reducing anal sex even with condom use) are most effective in reducing transmission among MSM, the messages most effective in promoting these behaviors, and the methods and settings in which these messages can be most effectively delivered.
A randomized social network HIV prevention trial with young men who have sex with men in Russia and Bulgaria.
To evaluate the effects of an HIV prevention intervention with social networks of young men who have sex with men (YMSM) in St. Petersburg, Russia and Sofia, Bulgaria.
                A two-arm randomized trial with a longitudinally-followed community cohort.
                Fifty-two MSM social networks were recruited through access points in high-risk community venues. Network members (n = 276) were assessed to determine risk characteristics, administered sociometric measures to empirically identify the social leader of each network, and counseled in risk reduction. The leaders of 25 experimental condition networks attended a nine-session program that provided training and guidance in delivering ongoing theory-based HIV prevention advice to other network members. Leaders successively targeted network members' AIDS risk-related knowledge and risk reduction norms, attitudes, intentions, and self-efficacy. Participants were re-administered risk assessment measures at 3- and 12-month follow-ups.
                Among changes produced, the percentage of experimental network members reporting unprotected intercourse (UI) declined from 71.8 to 48.4% at 3-month follow up (P = 0.0001). The percentage who engaged in UI with multiple partners reduced from 31.5 to 12.9% (P = 0.02). After 12 months, the effects became attenuated but remained among participants who had multiple recent sexual partners, the most vulnerable group. Little change was found in control group networks.
                Interventions that engage the identified influence leaders of at-risk YMSM social networks to communicate theory-based counseling and advice can produce significant sexual risk behavior change. This model is culturally pertinent for HIV prevention efforts in former socialist countries, as well as elsewhere for other hard-to-reach vulnerable community populations.