Despite decades of traditional prevention efforts based on behavior change and condom use, Ontario has seen over 700 new HIV infections annually over the past 10 years. Post-exposure prophylaxis (PEP) is one such approach, in which uninfected persons use 28 days of antiretroviral medications (ARVs) shortly after an HIV exposure to minimize the risk of acquiring HIV. PEP is highly efficacious, is considered a standard of care intervention based on medical and ethical grounds, and is supported by treatment guidelines. Yet several implementation challenges have limited its clinical and public health impact in Ontario, where no formal PEP policy exists. Our proposal seeks to optimize two aspects of delivering PEP for sexual exposures (nPEP). Results will inform the development of a standardized approach to nPEP both province-wide and elsewhere.

Thus study has pragmatic, multicenter randomized controlled trial using a 2x2 factorial design to determine whether the proportion of nPEP patients that successfully complete follow-up:

1. is higher among those receiving mobile phone-based text messaging support than among those receiving standard care; and
2. is non-inferior among those receiving care from a sexual health clinic nurse compared to those receiving hospital-based physician care.

The prospective, randomized, non-blinded, 2x2 factorial trial that will enroll 318 study participants in Toronto. In Intervention A, we will randomize half of study participants to a text messaging support service ('WelTel'), in which a trained, community-based counselor provides standardized weekly 'check-in' messages during their 12-week course of PEP follow-up. The other half will receive standard care, which does not include any form of active outreach or reminders outside of scheduled appointments. In Intervention B, we will randomize half of participants to receive nurse-led care for PEP follow-up at a local sexual health clinic; the other half will receive standard care by a hospital-based ID physician. The specific activities for each follow-up visit will be clearly defined in a medical directive. In keeping with Ontario legislation on medical directives, nurses will review cases with their authorizing physician or nurse practitioner on a routine basis.

Inclusion Criteria:

1. Be 18 years or older
2. Be known or presumed to be HIV-uninfected at baseline
3. Be initiated on PEP by a healthcare provider in the past six days for a sexual exposure to a known or suspected HIV-infected source
4. STAGE 1 only: Own a mobile phone with text messaging capabilities on which they are willing to potentially receive messages from the text messaging service
5. Be capable of communicating verbally and via text in English
6. Be planning to continue their follow-up locally or be willing to have follow-up study visits conducted remotely; either by telephone or via an encrypted video conferencing system (such as Zoom for healthcare).
7. Be referred to a sexual assault center and provided with necessary counselling and support services if presented for nPEP following sexual assault.

Exclusion Criteria:

1. Creatinine clearance <30 mL/min (using Cockcroft-Gault formula)
2. Enrolled in any other clinical trial of an HIV prevention intervention
3. Prior participation in this clinical trial for a previous episode of nPEP
4. Known co-infection with chronic hepatitis B at enrollment
5. Current or planned pregnancy or breastfeeding
6. Use of a medication whose co-administration with Biktarvy is contraindicated (dofetilide, carbamazepine, oxcarbazepine, phenobarbital, phenytoin, rifampin, rifampicin, rifabutin, rifapentine, modafinil, dexamethasone, metformin, St. John's Wort)
7. Concomitant use of HIV pre-exposure prophylaxis (PrEP)
8. Stage 2 only: Concomitant use of any non-prescription medication, supplement, vitamin or natural remedy which the patient is unwilling to discontinue during Biktarvy® administration