Characterization of HIV acquisitions during a large oral PrEP implementation study: insights from the ImPrEP study

OBJECTIVE: Characterization of HIV acquisitions during ImPrEP study. DESIGN: Implementation study among MSM and transgender women in Brazil, Mexico, and Peru (February 2018 to December 2020). METHODS: Participants used HIV rapid tests at enrollment and follow-up visits. HIV viral load on enrollment blood samples was used to identify acute HIV infections retrospectively. Participants with an HIV-negative rapid test at enrollment initiated oral PrEP. Adjusted logistic regression model assessed factors associated with acute HIV infections. We described characteristics of participants who acquired HIV during follow-up according to country, PrEP adherence measures, and virological outcomes. RESULTS: Acute HIV prevalence at enrollment was 0.5% (n = 43/9552). Factors associated included younger age and having any STI. Among 8714 participants (12 185.25 person-years of follow-up; median age 29 years; MSM: 94.8%; transgender women: 5.2%), 104 (1.2%) were diagnosed with HIV during follow-up. Among these, median HIV viral load was 12 257 copies/ml [interquartile range (IQR) 851-114 118]. One (1.8%) participant had K65R mutation and six (10.5%) M184V/I mutations. Median time from first PrEP dispensation to HIV diagnosis was 360 days, varying by country (P = 0.012). Only five participants (8.6%) had tenofovir intracellular levels consistent with at least four doses per week at HIV diagnosis visit. CONCLUSION: Our findings highlight low detection of acute HIV infection among those starting oral PrEP. Significant challenges in PrEP adherence were verified among young MSM and transgender women who acquired HIV during PrEP follow-up. Innovative approaches, such as long-acting PrEP formulations and tailored adherence support strategies, could play a crucial role in reducing HIV incidence among people using PrEP in Latin America.