Randomized controlled trials of individual-level, population-level, and multilevel interventions for preventing sexually transmitted infections: what has worked?

BACKGROUND Previous reviews of interventions to prevent sexually transmitted infections (STIs) focused mostly on human immunodeficiency virus (HIV) infection. We reviewed trials of interventions to prevent sexual transmission of any STI, employing a multilevel perspective. METHODS We searched MEDLINE, the Cochrane Central Register of Controlled Trials, and recent unpublished presentations through 2003, to identify randomized controlled trials of preventive STI interventions having systematic, objective measurement of STI outcomes. We classified trials according to intervention target and level of randomization (individual, group, or community); impact target (acquisition, transmission, or complications of STI); and primary intervention modality. RESULTS Of 83 trials identified, 41 met inclusion criteria, including trials of 28 individual-level, 9 group-level, and 4 community-level interventions. Among individual- and group-level interventions, 32 targeted acquisition, 4 targeted transmission, and 1 targeted complications of STI. The 4 intervention modalities most often used included behavior change (12 studies), vaccination (7 studies), use of topical microbicides (10 studies), and prophylactic, curative, or suppressive therapy (10 studies). Community-level interventions had multiple impact targets, and 2 interventions used multiple modalities. Only 1 intervention showed efficacy against sexual transmission of HIV, but 22 (53.7%) showed effectiveness against other STIs. CONCLUSION Although many interventions have been found to be effective against STIs, few have been replicated, widely implemented, or carefully evaluated for effectiveness in other settings.