Background:  Development of intravaginal HIV prevention products requires an understanding of sexually transmitted infection and vaginitis prevalence, specific sexual behaviors and genital hygiene practices in potential target populations. We assessed HIV risk behavior, genital hygiene practices, prevalence of sexually transmitted infections and vaginitis, HIV incidence, and retention in a cohort of HIV-uninfected female sex workers in urban Kenya in preparation for studies of intravaginal HIV prevention methods.

Methods:  Women aged 18 to 60, HIV^–, not pregnant, and who reported exchanging sex for money or gifts at least 3 times in the past month were enrolled and followed every 3 months for 6 months. HIV risk and vaginal hygiene behavior were described. Sexually transmitted infection prevalence and HIV incidence were analyzed by multivariate logistic regression analysis, controlling for demographic and behavioral factors.

Results:  We enrolled 200 women in the study. Mean age was 28 (range 18 to 55). Women reported an average of 4.2 paying sexual partners per day (range 0 to 7). Anal sex was not uncommon with 37% (74) of the women reporting a history of anal sex. Frequency of anal sex varied significantly by partner type, being most common with regular and casual partners and less common with primary partners, 35% (68 of 192) and 29% (54 of 188) vs 9% (6 of 64), 24% (17 of 71), and 21% (12 of 56) of women reported “never” using condoms for anal sex with regular or casual partners, respectively, compared to 9% (17 of 190) and 10% (18 of 87) for vaginal sex. Vaginal washing was universal. Prevalence of bacterial vaginosis was 37.5% (76 of 200), trichomoniasis 8.5% (18 of 200), vaginal candidiasis 7% (14 of 200), gonorrhea 6% (12 of 200), chlamydia 5.5% (11 of 200), syphilis 2.5% (5 of 200), herpes simplex virus 2 (HSV-2) seropositivity 72.2% (107 of 148). HIV incidence was 5.6 per 100 person-years (95%CI 0.82 to 10.38). Diagnosis of gonorrhea, chlamydia, trichomonas, or syphilis at baseline was predicted by reporting never having anal sex with casual partners (OR 3.32, 95%CI 1.2 to 8.55). HIV incidence was not clearly associated with any demographic or risk behavior. Retention was 93% at 1 month and 86% at 6 months. 

Conclusions:  Despite relatively low rates of some common sexually transmitted infections, this female sex worker population in urban Kenya had significant HIV incidence and may be appropriate for HIV prevention trials. The relatively high rates of anal sex and universal vaginal washing may complicate both safety and efficacy evaluation of intravaginal products and should be taken into account in trial design.