Background Trichomonas vaginalisis associated with adverse reproductive health outcomes, including HIV. Despite marked racial disparities, few studies have reported factors related to incident T. vaginalisinfection exclusively among young African-American women. The objective was to identify correlates of incident T. vaginalis infections among African-American adolescent females.

Methods Data were collected via audio computer self-interviews at baseline and every 6 months for 18 months from 701 African-American females (14–20 years) enrolled in an HIV prevention trial. Vaginal swabs were self-collected at each assessment and assayed for T. vaginalis, Chlamydia trachomatis and Neisseria gonorrhoeae using DNA amplification. Generalized estimating equations assessed associations between incident T. vaginalisinfection ,defined as a positive test result subsequent to a negative result or documented treatment, and sociodemographic characteristics, partner-level factors, HIV/STI-associated behaviours and STIs. Factors significant at p < 0.1 in bivariate analyses were entered into a multivariable model, adjusting for age and trial condition. The final model was obtained using backward selection procedures.

Results Of 606 (86.4%) participants who completed ≥ 1 follow-up assessment, an incident T. vaginalis infection was detected among 20.0% (n = 121). Trial condition was not independently associated with incident infection (p = 0.21). Significant correlates included: receipt of an increasing number of forms of government assistance (AOR: 1.20, 95% CI: 1.01, 1.42), cigarette smoking (AOR: 1.70, 95% CI: 1.08, 2.67), smoking marijuana an increasing number of days in the past 3 months (AOR: 1.02, 95% CI: 1.00, 1.04), concurrent C. trachomatis (AOR: 2.28, 95% CI: 1.43, 3.66) and N. gonorrhoeae (AOR: 5.99, 95% CI: 3.10, 11.57) infection and testing positive for T. vaginalis at the previous assessment (AOR: 4.56, 95% CI: 2.99, 6.96).

Conclusions Incident T. vaginalis infections were common. Strategies to reduce infection rates among this population may include improving partner notification and treatment services and addressing the role of substance use on sexual risk.