BONE: STAR (Switching to TAF Based Anti-Retroviral Therapy) Study

Inclusion Criteria: * Age 20 through 40 years (inclusive) at screening, verified per site SOPs * Able and willing to provide written informed consent to be screened for and to take part in the study. * Able and willing to provide adequate locator information, as defined in site SOPs * Previously participated in the BONE: CARE study. Additional women will be recruited from the health centers where the BONE: CARE participants were receiving HIV care, and these will be matched to those from the BONE: CARE cohort based on age, duration on ART and contraception use. * Per participant report, plans to stay in the study catchment area in the next 24 months * Per participant report, willing to continue using similar contraceptive method as in the BONE: CARE study. Exclusion Criteria: * Currently pregnant/ breastfeeding or was pregnant/ breastfeeding in the last 6 months prior to screening * Intentions to get pregnant in the next two years * History of active tuberculosis * Pathologic bone fracture not related to trauma (ever) * Has pre-existing condition known to affect bone metabolism (e.g. thyrotoxicosis, tuberculosis, diabetes mellitus, liver or renal disease) * Is taking the following medications known to interfere with bone metabolism (steroids, anti-convulsants, bisphosphonates, cancer drugs, etc.).