Characterizing Event-Driven PrEP Use and Investigating its Association with Experiences of PrEP-Related Barriers Among a US National Sample of PrEP Users.

After a decade of implementation in the US, PrEP uptake remains underutilized by communities that would greatly benefit from it. Event-Driven (ED) PrEP is a potential avenue to increase uptake, however very little is known about its use in the US. We analyzed data derived from Together 5000, an internet-based U.S. national cohort of Sexual and Gender Minority (SGM) individuals aged 16-49 years and at risk for HIV. First, we looked at predictors of ED PrEP use using a framework based on current US-based PrEP implementation-related variables. Then, we explored whether experiencing certain types of barriers were associated with choice of ED PrEP over daily PrEP using logistic regression analysis. Our findings showed that variables related to education and sexual behaviors were associated with ED PrEP choice, while experiencing barriers to daily PrEP had no effect. We found a gradient effect with education, where individuals who reported having some college had 3 times the odds of taking ED PrEP, those reporting a bachelor's degree had 3.25 times the odds, and those with graduate school education had 7.56 times the odds of choosing ED PrEP compared to those with a high school diploma or less. Individuals who reported having 2 or more hours of lead time for sex had 3.35 times the odds of using ED PrEP (aOR = 3.35, 95% CI 2.23-5.47). Participants who reported having an STI within the last 6 months had 60% lower odds of using ED PrEP (aOR = 0.4, 95% CI 0.2-0.72). The use of ED PrEP is a promising pathway for expanding PrEP due to its success and protection levels. Our studies indicated that educational background and behavior influence PrEP choice. Ensuring PrEP candidates and users have access to information about new PrEP types may increase uptake and support implementation efforts.