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Pre-exposure prophylaxis (PrEP) has the potential to significantly reduce HIV incidence among men who have sex with men (MSM) in the United States. However, the extent to which suboptimal PrEP adherence and retention in care may limit successful implementation is unknown. An agent-based model was used to represent the entire population of MSM in Rhode Island from 2013 to 2017. The impact of potential interventions to improve PrEP adherence and retention in care on HIV transmission was evaluated. Demographics, behaviors, and PrEP adherence and retention in care rates were based on local clinical data. We assumed that 20% of HIV-negative MSM had ever taken PrEP. The primary outcome was HIV incidence over the 5-year period. The model included 23,815 MSM with an estimated 4.1% HIV prevalence based on local surveillance data. An estimated 173.1 new infections occurred over 5 years [95% simulation interval (SI): 171.5–174.7], including 29.1 new infections among individuals who had ever initiated PrEP (95% SI: 28.6–29.7). Interventions that improved retention in PrEP care by an odds of 5.0 compared with the base case maximized reductions in HIV incidence among MSM who had ever initiated PrEP by 37.5%. Interventions focusing on improving PrEP adherence had little to no effect on HIV incidence, regardless of intervention efficacy. Retention in care is a critical component of the PrEP care continuum. Interventions that improve retention in PrEP care may lead to greater reductions in population-level HIV incidence compared with interventions focused exclusively on adherence. [ABSTRACT FROM AUTHOR]

Several studies suggest that the increase in sexually transmitted infections (STIs) among men who have sex with men (MSM) could be due, in part, to human immunodeficiency virus (HIV) risk reduction strategies, which include engaging in oral sex over anal sex. The aims of this study were to evaluate oral sex behaviors and STI diagnoses and to investigate the potential dual role of oral sex as being protective for HIV, yet perpetuating STI transmission among MSM. We analyzed records from 871 MSM presenting to the Rhode Island STI Clinic between 2012 and 2015. We compared outcomes in men engaging in two HIV protective oral sex behaviors: (1) HIV/STI outcomes by men engaging only in oral sex versus those that did not, and (2) HIV/STI outcomes by men engaging in condomless oral sex with 100% condom use for all other sex acts versus those that did not. Men engaging in HIV protective oral sex behaviors were more likely to be HIV negative compared to men not engaging in them (99% vs. 93%, p < 0.01). In contrast, there was no significant difference in STI diagnoses between those that engaged in HIV protective oral sex behaviors and those that did not. The findings provide evidence to support the unique duality of oral sex: decreased risk for HIV and perpetuation of STI risk. Promotion of routine STI testing, including extragenital sites, is critical to address STI prevention among MSM. In the age of HIV prevention, addressing the ambiguous risks of discrete sex acts would be beneficial for both HIV and STI prevention education for MSM. [ABSTRACT FROM AUTHOR]