P367 Hormonal contraception and risk of STIs and bacterial vaginosis in south african adolescents: a randomized trial

Background Young women in sub-Saharan Africa are at high risk for sexually transmitted infections (STIs) and often rely on hormonal contraception (HC) to prevent unwanted pregnancies. Some observational data suggest that HC might affect STI risk. We examined the impact of three HC methods on the adolescent STI incidence and BV prevalence in a randomized trial. Methods 130 adolescent females aged 15 to 19 from Cape Town were enrolled and randomized into three study arms: 1. injectable norethisterone enanthate (NET-EN), 2. combined oral contraceptives (COCs) or 3. combined contraceptive vaginal ring (CCVR) for 16 weeks. Participants then switched to a second HC for a final four months. Vaginal samples were collected at baseline, crossover and exit for STI (chlamydia, gonorrhoea, mycoplasma and trichomoniasis) and bacterial vaginosis (BV) testing by Nugent scoring. Results At baseline, the BV and STI prevalence was 44% and 42%, respectively. There were no significant differences in STI incidence between study arms at crossover, however in an according to protocol analyses, participants using COCs were significantly less likely to present with any STI than participants using either NET-EN (OR 0.22, 95% CI 0.06–0.71, p=0.017) or CCVR (OR 0.21, 95% CI 0.05–0.69, p=0.015). Specifically, participants on CCVR were more likely to be infected with N. gonorrhoea (OR 11.7, 95% CI 2.0–224, p=0.025). These associations stayed significant after adjusting for sexual risk behaviour, including condom use. There was a decreased prevalence of BV in the COC arm and an increased BV prevalence in the NET-EN and CCVR arms at crossover, but these differences were not statistically significant. Conclusion Use of COCs was associated with lower BV prevalence and STI incidence compared to NET-EN and CCVR use. Disclosure No significant relationships.