Intervention: Tenofovir
Trial phase: Phase 2
SMILES: C[C@H](Cn1cnc2c(N)ncnc21)OCP(=O)(O)O
Sex: All
Age groups: Child | Adult
Healthy volunteers: Accepts Healthy Volunteers
Participants at risk: 148
Group description: All participants will take Truvada, once daily by mouth for the first 12 weeks of the study. After Week 12 of the study, only participants who indicate a willingness to use Truvada PrEP and who do not have any medical reasons not to do so will continue to receive the Truvada tablets through Week 48.

Truvada: Fixed-dose combination tablet containing 200 mg of FTC plus 300 mg of TDF, taken once daily by mouth.
Eligibility criteria:
Inclusion Criteria:

Age 15 to 19 years (inclusive) at screening, verified per study site standard operating procedures (SOPs)
Able and willing to provide written informed consent/assent (age dependent) to be screened for and to take part in the study
Have a guardian who is able and willing to provide written informed consent for his or her child to be screened for and to take part in the study
Able and willing to provide adequate locator information, as defined in site standard operating procedures (SOPs)
HIV-uninfected based on testing performed by study staff at screening and enrollment
Sexually active, as defined as a minimum of one act of (penile vaginal) sexual intercourse in the last 12 months, per self-report
(For female participants) Negative pregnancy test at screening and enrollment and, per participant report, does not intend to become pregnant in the next 12 months
(For female participants) Using an effective method of contraception at enrollment, and intending to use an effective method for the study duration; effective methods include low dose oral, implant, or injectable hormonal methods.
Does not report intention to relocate out of the study area during the course of the study
Does not have job or other obligations that would require long absences from the area (for more than 4 weeks at a time)
Willing to undergo all study-required procedures
At screening and enrollment, agrees not to participate in other research studies involving drugs or medical devices for the next 12 months

Exclusion Criteria:

Participants who meet any of the following criteria, at baseline, are excluded from the study:

As determined by the Site Investigator, any significant uncontrolled active or chronic disease process such as but not limited to diabetes, hypertension, and other diseases involving the cardiovascular, pulmonary, gastrointestinal, genitourinary, musculoskeletal, and central nervous systems
Confirmed Grade 2 or greater hypophosphatemia
Presence of serious psychiatric symptoms (e.g., active hallucinations)
Visibly distraught at the time of consent (e.g., suicidal, homicidal, exhibiting violent behavior)
Intoxicated or under the influence of alcohol or other drugs at the time of consent
Acute or chronic hepatitis B infection (i.e., if hepatitis B surface antigen positive)
Hepatitis B seronegative and refuses vaccination
Renal dysfunction (creatinine clearance less than 75 ml/min); Use Cockroft-Gault equation as detailed in the protocol
Urine dipstick for protein and glucose, excluding values of "1 +" or greater
Any history of bone fractures not explained by trauma
Any Grade 2 or greater toxicity on screening tests and assessments
Concurrent participation in an HIV vaccine study or other investigational drug study
Known allergy/sensitivity to the study drug or its components
Use of disallowed medications (as detailed in the protocol)