This is an observational study of HIV-1 negative individuals who participated in demonstration projects or clinical studies and took daily Emtricitabine/Tenofovir Disoproxil Fumarate (FTC/TDF, Truvada®) for pre-exposure prophylaxis (PrEP). All individuals were enrolled and followed as described in the parent PrEP demonstration project or clinical study protocol until study completion, HIV-1 infection, discontinuation due to an adverse event, lost to follow-up, or administrative censoring.

In the protocols of the parent PrEP observational or clinical studies, participants had follow-up visits on average every 3 months for evaluation of adherence, renal and bone adverse events, and HIV-1 infection status. Adherence was determined by the specific FTC/TDF drug level measurement(s) outlined in the parent protocol.

Gilead had collected data from 21 global PrEP demonstration projects and clinical studies for over 7,000 Truvada for PrEP users who had at least one measurement of adherence. Data from the different contributing studies were pooled for statistical analyses by Gilead.

Inclusion Criteria:

• Participants in an FTC/TDF for PrEP observational or clinical study
• HIV-1 negative individual at the time of enrollment in a demonstration project or clinical study
• Participants with at least one measurement of tenofovir-diphosphate (TFV-DP) in dried blood spot (DBS) or tenofovir (TFV) in plasma

Exclusion Criteria:

• This is an observational study and will collect HIV-1 infection and resistance information along with renal or skeletal adverse events without intervention.

Seven thousand (7000) HIV-1 negative adults (any sex/gender, including transgender, pregnancy) who are participating in observational or clinical studies on FTC/TDF for PrEP