The incidence of STIs is higher among men who have sex with men, or MSM, who take daily pre-exposure prophylaxis, or PrEP, for HIV prevention compared with those who use event-driven PrEP, according to recently published study findings.
Researchers said the finding suggests the need to tailor prevention interventions according to sexual behavior profiles.
“PrEP is a powerful tool to prevent HIV infections. PrEP uptake is slowly expanding in an era of increasing STI incidence among MSM in several geographical areas, which predates the introduction of PrEP,” Elske Hoornenborg, MD, of the Department of Infectious Diseases at the Public Health Service of Amsterdam, and colleagues wrote. “Available data on related outcomes, such as changes in STI incidence and sexual behavior, are limited and conflicting, and the causal link between these outcomes and PrEP use is unclear. Whether STI incidence increases after initiation of PrEP and during PrEP use is not yet established.”
Hoornenborg and colleagues conducted Amsterdam PrEP (AMPrEP), a demonstration study that assessed the incidence of HIV and STIs and the sexual behavior of PrEP users at the STI clinic of the Public Health Service of Amsterdam. Participants were transgender women and MSM aged 18 years or older who were HIV-negative and reported having condomless anal sex with casual partners, at least one bacterial STI, use of post-exposure prophylaxis after a sexual risk incident or an HIV-positive sexual partner with detectable viral load.
According to the study, participants chose daily or event-driven PrEP regimens, were tested every 3 months for HIV and STIs and completed self-administered questionnaires about sexual behavior at each visit.
Between Aug. 3, 2015, and May 31, 2016, Hoornenborg and colleagues recruited 365 MSM and two transgender women for the analysis, including 269 (73%) who chose daily PrEP and 98 (27%) who chose event-driven PrEP. According to the study, two individuals in the daily PrEP group became HIV positive, and the overall HIV incidence rate was 0.30 per 100 person-years (95%, CI = 0.07–1.19). Additionally, the researchers found that 253 participants were diagnosed with one or more STI during the first 2 years, and that the STI incidence did not change over time.
According to the study, STI incidence was 41% lower in the event-driven PrEP group than the daily PrEP group (adjusted incidence rate ratio [aIRR] = 0.59; 95%, CI = 0.46–0.75).
“We confirm that daily and event-driven PrEP regimens are effective for the prevention of HIV, despite a high incidence of STIs among MSM using PrEP in the Netherlands,” the authors concluded. “Regular HIV and STI testing remain of great importance among MSM using PrEP. Frequency of STI testing, and behavioral and other STI prevention interventions might be tailored specific to sexual behavior. These public health strategies need to be considered by both clinicians and policymakers.” – by Caitlyn Stulpin
Disclosures: Hoornenborg reports receiving advisory board fees from Gilead Sciences and speaker fees from Janssen-Cilag, both paid to her institution. Please see the study for all other authors’ relevant financial disclosures.