The goal of this randomized controlled trial is to test the effectiveness of "TIARAS," a trauma intervention designed to reduce HIV acquisition risk among women who inject drugs (WWID). To be eligible for this study, participants must have been prescribed pre-exposure prophylaxis (PrEP), a medication taken to prevent HIV, at Prevention Point Philadelphia, a large harm reduction agency located in Philadelphia (PA, USA), or Courage Medicine, a nonprofit health services clinic located in Philadelphia (PA, USA).

Enrollment in this study lasts for 12-months so that we can see if TIARAS reduces HIV risk immediately after the intervention ends and whether these effects last over time. During the first 3 months, participants engage in contingency management (CM), an evidenced-based intervention to reduce drug use and HIV risk. We will use CM to encourage engagement in PrEP care as well as stimulant/opioid abstinence. Also during the first 3-months, participants are randomly assigned to complete expressive writing exercises to address a previously undisclosed trauma or neutral writing exercises. Half of the participants will be assigned to the trauma writing group and the other half will be assigned to the neutral writing group.

To understand the impact of TIARAS on HIV risk, we will collect and analyze data from surveys, interviews, and biological specimen during the 12-month study period. Our main questions are:

• Does participation in TIARAS reduce HIV risk among WWID?
• If observed, how long do beneficial effects last?
• How and why do WWID experience benefits from TIARAS?

In the United States, recent outbreaks coast-to-coast forewarn of a possible resurgence of HIV, especially among women who inject drugs (WWID), particularly if access, uptake, and adherence to effective harm reduction tools remain sub-optimal. Pre-exposure prophylaxis (PrEP) is a user-driven method that safely and effectively prevents HIV. While we have shown that cisgender WWID consider PrEP beneficial and are willing to accept a prescription, consistent with the well-known SAVA syndemic framework, social stigma, economic insecurity, traumatic experiences (or the threat of violence), and drug use greatly undermined their agency to prioritize and adhere to PrEP. This trauma-informed randomized control trial (RCT) will address the urgent need for HIV prevention interventions, informed by the SAVA framework, that produce durable reductions in HIV risk among WWID. We will integrate contingency management (CM), a proven strategy to reduce drug use and HIV risk, and expressive writing (EW), a safe and effective approach for addressing trauma symptoms, in order to test whether EW delivered during CM (EW+CM) produces durable reductions in HIV acquisition risk compared to an attention-control condition. We will leverage our partnership with Prevention Point Philadelphia (PPP), the largest syringe exchange in the mid-Atlantic, and Courage Medicine to recruit 240 WWID who will (re)initiate PrEP at PPP or Courage Medicine. Once enrolled they will immediately begin a 3-month CM period that provides incentives for directly observed daily oral PrEP doses or confirmed injectable PrEP doses, stimulant/opioid abstinence (measured thrice weekly through urine screening), and completion of four writing sessions. After a run-in period, WWID will be randomized to either EW+CM (n=120) or Neutral Writing+CM (n=120). Follow-up assessments will occur at 3-, 6-, and 12-months post-randomization and will include objective measures of PrEP adherence over time. A subset of WWID from both arms will complete qualitative interviews at 3- and 12-months. All study activities and daily PrEP dispensing will occur at PPP. The specific aims are to: (1) Determine the efficacy of EW+CM for improving the proportion of participants achieving reductions in HIV acquisition risk (operationalized as the proportion of WWID reporting syringe sharing or condomless sex during objectively measured periods of PrEP non-adherence) at 12 months. (2) Examine key secondary outcomes such as greater PrEP persistence, reductions in substance use, PTSD symptoms, and depression, as well as entry into drug treatment over 12 months. (3) Evaluate the pathways through which the intervention operates using qualitative interviews, mediation analysis (e.g., emotional expression and processing in EW essays), and moderation analysis (e.g., more pronounced among those with higher PTSD severity at baseline). This RCT could have an exceptional impact by yielding one of the first evidence-based interventions to address HIV acquisition risk in the era of PrEP among WWID.

Inclusion Criteria:

a) HIV-negative cisgender female, b) age ≥ 18 years, c) speaks/reads English d) reporting past 6 months day non-prescription injection drug use and any of the following: NEW PrEP PATIENT: prescribed daily oral or injectable PrEP at Prevention Point Philadelphia or Courage Medicine within 30 days. For injectable PrEP, they will be considered new if they have received a prescription but are within two weeks of receiving their first injection. or NON-ADHERENT DAILY ORAL PrEP PATIENT: initiated PrEP at Prevention Point Philadelphia or Courage Medicine 30 or more days ago who reports any non-adherence or reports consistent adherence but has PrEP-related drug levels indicating non-adherence (verified with urine-based tenofovir testing) or NON-ADHERENT INJECTABLE PrEP PATIENT: initiated injectable PrEP at Prevention Point Philadelphia or Courage Medicine but is 8 or more days late to receive their next injection (verified in participant's electronic medical record)

Exclusion Criteria:

a) Unable to provide informed consent; b); unwilling or unable to return to the SSP daily for the next 90 days; c) unwilling to provide specimen for PrEP-related clinical monitoring and adherence monitoring; d) pregnant.

Cisgender females eligible

Study personnel who administer survey assessments will be blinded to study participants' assignment to the expressive writing group (treatment) or the neutral writing group (control).