Acknowledgements
We thank all the women who participated in this study for their devotion to the study and the time they committed to research procedures. This work and the Evidence for Contraceptive Options and HIV Outcomes (ECHO) Study were made possible by the combined generous support of the Bill & Melinda Gates Foundation (Grant OPP1032115), the American people through the United States Agency for International Development (Grant AID-OAA-A-15–00045), the Swedish International Development Cooperation Agency (Grant 2017/762965–0), the South Africa Medical Research Council, and the United Nations Population Fund. Contraceptive supplies were donated by the Government of South Africa and US Agency for International Development. Funding to support this ancillary study of biological mechanisms was from the US National Institute of Child Health and Human Development under grant numbers 5R01HD089831 (R.H., H.B.J.). B.P.B. was also supported by F32HD102290 and K99HD106861. The content is the sole responsibility of the authors and does not necessarily represent the official views of the study funders.