Objectives Young women in sub-Saharan Africa are at high risk of STIs and unintended pregnancies, yet hormonal contraceptive (HC) use may affect STI risk. We compared the influence of three HCs on the incidence and prevalence of STIs and bacterial vaginosis (BV) in South African adolescents.
Methods One hundred and thirty adolescents between 15 and 19 years were randomised to the injectable norethisterone enanthate (Net-En), combined oral contraceptives (COC) (Triphasil or Nordette) or a combined contraceptive vaginal ring (CCVR; NuvaRing) for 16 weeks (clinicaltrials.gov/NCT02404038). Vaginal samples were collected at baseline and 16 weeks post contraceptive initiation for STI and BV testing.
Results In an intention-to-treat analysis, no significant differences in BV prevalence were found between study arms. The overall incidence of any STI at follow-up was high: 16.2% in the COC arm; 25.7% in the Net-En arm; and 37.1% in the CCVR arm. The incidence rate (IR) of any STI was similar between Net-En (IR 0.74 (95% CI 0.34 to 1.41)) and the oestrogen-containing contraceptives (IR 0.78 (95% CI 0.47 to 1.22)). A lower IR of Chlamydia trachomatis (incidence rate ratio (IRR) 0.68 (95% CI 0.19 to 1.99)) and Neisseria gonorrhoeae (IRR 0.25 (95% CI 0.01 to 1.35)) but a higher IR of Mycoplasma genitalium (IRR 16.0 (95% CI 2.96 to 400)), was observed in the Net-En arm compared with the oestrogen-containing contraceptives, although the overall incidence of M. genitalium was low (4.7%). In an exploratory analysis, the risk of any STI and N. gonorrhoeae was lower in the COC arm compared with CCVR. A per-protocol analysis yielded similar results.
Conclusion Our results suggest that use of Net-En may be associated with increased risk of M. genitalium compared with oestrogen-containing contraceptives but not with overall STI risk. COC use may decrease STI risk relative to CCVR.
- hormonal contraception
- bacterial vaginosis
- clinical trials
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Handling editor Nicola Low
L-GB and HBJ contributed equally.
Contributors Conceived and designed the experiments: HJ, J-AP, CB, LM, ML, KG and L-GB. Designed and recruited the UChoose cohort: L-GB, KG, TP, SB. Processed samples and performed wet lab experiments: CB, SZJ, INK, RE, A-UH, HG. Performed STI and BV testing: VM. Analysed the data: CB, KL, HJ. Wrote the manuscript: CB, J-AP, HJ, L-GB, KG.
Funding This work was supported by grants from National Institutes of Health R01 HD083040 to HJ and J-AP and R01 AI094586 to L-GB and South African Polio Research Foundation postdoctoral award to CB.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Approval for the study was granted by the Research Ethics Committee at the University of Cape Town (HREC 801/2014) and was conducted in full compliance with South African Good Clinical Practice (SA-GCP), International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) 76 GCP guidelines and International Committee of Medical Journal Editors (ICMJE) guidelines. All participants 18 years or older provided informed written consent, while assent was obtained from participants younger than 18 years old and informed written consent from parents or legal guardians.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement The de-identified datasets analysed for the study are available from the corresponding author on reasonable request.