Clinical Research Directory

Inclusion Criteria: All adolescent and adult young women who meet all the following criteria are eligible for inclusion in this study: * Age 13-34 years, inclusive. * In good health as determined by past medical history, medication use, and targeted physical examination, * If not living with HIV, negative HIV test conducted at screening * If living with HIV, on an antiretroviral regimen for ≥3 months * Report at least two of the following: * Treatment for a curable STI (not including HIV) in the past 12 months prior to screening. * Self-report of condomless (oral, vaginal, and/or anal) intercourse at least once in the 30 days prior to screening * Has had two or more partners in the past 6 months * ≥ 45 kilograms (99 pounds) in weight * Anticipate living in the study area for 12 months and no plans for travel away from the study site for a time period that would interfere with product resupply and study participation * Willing to undergo all required study procedures that may include Directly/Video observed therapy (D/VOT); and * Provide written informed consent to participate in the study * If of legal age or otherwise able to provide independent informed consent as determined by local law and consistent with Institutional Review Board (IRB)/Ethics Committee (EC) policies: Willing and able to provide written informed consent for study participation. * If not of legal age or otherwise not able to provide independent informed consent as determined by local law and consistent with IRB/EC policies: Parent or legal guardian is willing and able to provide written informed consent for study participation and potential participant is willing and able to provide written assent for study participation. Exclusion Criteria: All adolescent and adult young women who meet any of the following criteria will be excluded from this study: * Is male. * Positive NAAT for CT or NG or with evidence of untreated syphilis infection. * Documented history of tetracycline allergy or self-reports an allergy to tetracyclines. * Current (within 30 days of Enrollment) or anticipated use of a medication with a contraindicated interaction to doxycycline (e.g., iron, barbiturates, phenytoin, lithium, carbamazepine, systemic retinoids, warfarin). * Current or planned use of doxycycline for a prolonged period (\> 2 weeks) in the 30 days prior to enrollment, including current prescription for doxycycline for STI prophylaxis. * Prolonged antibiotic use (\> 2 weeks) within the last 30 days prior to enrollment. * Pregnant, or breastfeeding. * Co-enrollment in any other concurrent interventional research or studies that may interfere with this study, unless approved by the Protocol Team in writing. * Any other medical condition, medical/behavioral intervention, or other conditions that, in the opinion of the clinical site Principal Investigator/Investigator of Record (PI/IoR) or designee, could interfere with adherence to study procedures or compromise interpretation of study results.