Increased HIV incidence during Event-Driven PrEP compared to Daily PrEP in the Netherlands

Background Clinical trials demonstrated high efficacy of daily and event-driven oral pre-exposure prophylaxis (PrEP) in HIV prevention. Event-driven PrEP involves taking two tablets before and two times one tablet after sexual contact (2-1-1/on-demand). While both are implemented in Dutch clinical practice, evaluating real-world effectiveness requires large-scale data from routine clinical care. This study compared HIV incidence between daily and event-driven PrEP in the Netherlands. Methods We used surveillance data from the Dutch national PrEP program (August 1, 2019-December 31, 2025). Individuals [≥]16 years with [≥]1 follow-up consultation after PrEP initiation were included; PrEP regimen since last visit was recorded at each visit. Person-time was modeled as time-varying based on the regimen reported at each consultation. HIV incidence rates were calculated per 100 person-years and Cox proportional hazards models estimated hazard ratios between regimens for HIV acquisition, adjusted for sociodemographics, sexual behavior, and history of sexually transmissible infections. Findings 16,469 individuals (15,843 men who have sex with men, 579 transgender and gender diverse persons, 45 women and two men who have sex with women) initiated PrEP and had [≥]1 follow-up visit (median follow-up 2.0 years (IQR=0.8-4.0)). Median age was 33 years (IQR=27-44). 49 PrEP users were diagnosed with HIV over 41,092 person-years (IR=0.12/100 py;95%CI=0.09-0.16), of whom 42 event-driven users (IR=0.20/100 py;95%CI=0.15-0.27) and seven daily PrEP users (IR=0.04/100 py;95%CI=0.02-0.07). In multivariable Cox regression, event-driven PrEP use was associated with a higher hazard of HIV acquisition (aHR=7.0;95%CI=3.0-16.4). Interpretation Despite overall low HIV incidence, the incidence rate in the Dutch national PrEP program was seven-fold higher during event-driven PrEP use compared to daily, which may be due to lower adherence. These findings denotes that, in real-world settings, improved person-centered counseling is needed for individuals interested in, or using event-driven PrEP. Research should identify domains and preferred methods of support. Funding None for this study.