The Real-World Effectiveness of Human Immunodeficiency Virus Pre-Exposure Prophylaxis in Adults in Alberta, Canada: A Retrospective Population-Based Cohort Study.

Abstract

Background: In clinical trials, pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate-emtricitabine (TDF/FTC) or tenofovir alafenamide-emtricitabine (TAF/FTC) is up to 99% efficacious in preventing human immunodeficiency virus (HIV) infection. The real-world effectiveness of PrEP has not been extensively evaluated in Canada. Methods: This population-based cohort included adults without HIV as determined by viral serology and ICD-9/ICD-10 codes from Alberta with ≥ 3 months of PrEP prescriptions. It used provincial administrative data. Patients were followed from their first PrEP prescription until diagnosed HIV infection or censoring. Cox proportional hazard models were used to identify independent predictors of HIV infection. Results: A total of 4750 adults with a mean (SD) age of 35.9 (11) years of which 8% were female were prescribed PrEP including TDF/FTC (97.5%) or TAF/FTC (2.5%). There were 335 HIV infections (92.9% effectiveness) over median cohort follow-up of 1.0 years (IQR 1.9) with 4.89 (95% CI 4.38, 5.44) HIV infections per 100 patient years. Age (HR 1.04, 95% CI 1.03-1.05 per 1 year increase), male sex (HR 0.34, 95% CI 0.27-0.44), CKD Stage G3 (HR 2.39, 95% CI 1.82, 3.14), SES (4th and 5th quintiles versus 1st quintile), drug use (HR 2.11, 95% 1.45, 3.08), and history of STI (HR 0.45, 95% CI 0.29, 0.72) were independent predictors of HIV infection. The HIV incidence decreased to 1.5 (95% CI 1.2, 1.8) and 0.6 (95% CI 0.4, 0.9) per 100 patient years in cohorts with negative baseline HIV serology with 180 and 30 days prior to index PrEP prescription. Conclusion: HIV PrEP appears to be effective for preventing HIV infection in this real-world population-based study in Alberta, Canada. Strategies to mitigate residual HIV risk in PrEP users are needed.