Low prevalence of bacterial vaginosis in Kenyan adolescent girls and rapid incidence after first sex.

BACKGROUND: Bacterial vaginosis is a risk factor for sexually transmitted infections, including HIV. Adult African women have a high prevalence of bacterial vaginosis, but it is not known when first bacterial vaginosis occurs. OBJECTIVE: This study aimed to describe bacterial vaginosis in younger African women, before and after first sex, and to determine the incidence of bacterial vaginosis and significant correlates of bacterial vaginosis incidence and recurrence. STUDY DESIGN: In a prospective observational cohort study enrolling adolescents with limited sexual experience, young women aged 16 to 21 years were recruited in Thika, Kenya. Eligible participants were HIV and herpes simplex virus 2 seronegative and reported 0 or 1 lifetime sexual partner. The Nugent score was determined at quarterly visits from vaginal Gram stains. The trends in bacterial vaginosis were described over time; hazard ratios were calculated using Cox regression, and relative risk of bacterial vaginosis was estimated using generalized estimating equations and Poisson regression. RESULTS: A total of 400 participants with a median age of 18.6 years (interquartile range, 16-21) were enrolled. Of note, 322 participants (80.5%) reported no history of sex, whereas 78 participants (19.5%) reported sex with 1 partner. At enrollment, bacterial vaginosis (Nugent score of ≥7) was uncommon (21/375 [5.6%]). Overall, 144 participants had bacterial vaginosis at least once, for an incidence rate of 16.5 cases per 100 person-years. Before first sex, bacterial vaginosis was present at 2.8% of visits, compared with 13.7% of visits after first sex. An adjusted model of bacterial vaginosis incidence observed that first sex was associated with more than a 2-fold increased bacterial vaginosis risk (adjusted hazard ratio, 2.44; 95% confidence interval, 1.25-4.76; P=.009). Chlamydia diagnosis (adjusted hazard ratio, 1.73; 95% confidence interval, 1.1-2.8; P=.02), and herpes simplex virus 2 seropositivity (adjusted hazard ratio, 2.88; 95% confidence interval, 1.17-7.09; P=.021) were both associated with incident bacterial vaginosis. A multivariate generalized estimating equation model, including all episodes of bacterial vaginosis, demonstrated risk factors, including first sex, sexually transmitted infections, urban residence, recent sex, and no income; the most important risk factor was first sex (adjusted relative risk, 1.92; 95% confidence interval, 1.12-3.31; P=.018). The probability of bacterial vaginosis increased with each subsequent episode; mean Nugent scores increased after each bacterial vaginosis episode. CONCLUSION: Using detailed longitudinal observation, this study found that Kenyan adolescents have almost no bacterial vaginosis before first sex and that initiation of sexual activity was the strongest risk factor for both prevalent bacterial vaginosis and incident bacterial vaginosis.

Adolescent Girls and Young Women in Kenya Demonstrate Rapid STI Incidence Following First Sex: Data From a Longitudinal Cohort.

PURPOSE: Adolescent girls and young women (AGYW) are disproportionately affected by STIs. Observation of life course events can describe behavioral and biological factors associated with STI risk. METHODS: Sexually inexperienced AGYW aged 16-20 years in Kenya were followed for five years. Quarterly visits assessed for C. trachomatis (CT), N. gonorrhea (GC), and T. vaginalis (TV), bacterial vaginosis (BV), HSV-2, and HIV. Sexual activity was self-reported but amended if incongruent with results from STI, pregnancy, or any other testing. Cox regression and Generalized Estimating Equation models were used to determine hazard ratios (HRs) and relative risks (RRs) of STI. RESULTS: During follow-up, 293 of 400 participants reported sex, 163 AGYW experienced an STI, and 72 participants had multiple STIs. Among 163 participants that experienced an STI, there were a total of 259 visits where STIs were detected, 78% (n = 201) of which included CT. Cox regression found participants with BV had over two-fold higher risk of first STI acquisition (adjusted hazard ratio (aHR): 2.35; 95% confidence interval (CI) 1.43-3.88; p = .001). Increased risk for first STI episode was associated with a new partner (aHR: 3.16; 95% CI 1.59-6.28; p = .001). AGYW who did not disclose sexual activity had the highest risk (aHR: 3.60; 95% CI 1.93-6.70; p < .001). Condom use was low, with 21% reporting condom use with sex. GEE analysis of all STIs including incident, prevalent, and recurrent, confirmed these risk factors. DISCUSSION: During the critical years after first sex, AGYW with BV, new sexual partners, and those who did not disclose sexual activity were at highest risk for STI events, especially CT.