This work was presented at the Feb 2017 Conference of Retroviruses and Opportunistic Infections (CROI) in Seattle, Washington.
Background: Adolescent sexual minority males (ASMM) in the US have high HIV risk- one estimate is 7% prevalence at age 18-and thus may be good candidates for preexposure prophylaxis (PrEP). However, targeting PrEP to ASMM raises many issues, including identifying behavioral indications for prescription that are feasible to implement in clinical practice and which provide high epidemiological impact and efficiency.
Methods: We modified our mathematical model of HIV transmission among adult MSM to focus on ASMM. We explored 7 scenarios for PrEP indications, based on age (13-18 vs. 16-18) and sexual behavior (planning to initiate anal intercourse [AI], already initiated AI, >5 or >10 condomless AI acts in the past 6 months). The median duration remaining on PrEP was 48 weeks, with adherence rates based on preliminary results from the ongoing ATN113 trial. We considered 5 levels of coverage. Outcomes were % of infections averted (PIA) and number needed to treat (NNT, person-years on PrEP per infection averted).
Results: Our base scenario (40% coverage, indications = sexually active ASMM aged 16-18, PrEP initiated on average 6 months after debut) prevented 35.1% of infections, with an NNT of 33. Dropping eligibility age to 13 increases both the PIA (44.4%) and NNT (38) moderately. Initiating PrEP shortly before AI debut increased both further (48.3%, 41). Focusing on adolescents with the largest number of recent condomless AI acts yielded comparable PIA (35.2%-47.6% across scenarios), but much lower NNT values (27-32). Changing coverage demonstrated non-linearly increasing PIA values (20% coverage = 18.7% PIA, 60% coverage = 47.6% PIA), with slightly higher efficiency (lower NNT) for lower coverage (20% coverage = 33, 60% coverage = 36).
Our model demonstrates that PrEP could significantly reduce HIV incidence among U.S. ASMM. There are multiple ways to achieve high epidemiological impact and efficiency, although each involves challenges to both public health infrastructure (increasing PrEP coverage capacity for ASMM) and clinical practice (having clinicians assess relevant sexual histories). The strategies targeted to the highest risk ASMM achieve levels of efficiency similar to some scenarios considered in our recently published adult MSM model.
Conclusion: These results underscore the importance of developing approaches to reach and screen ASMM with the highest HIV risk, and to provide tailored support for their adherence and retention while on PrEP.
Check out the poster below!
Downloadable Files:CROI 2017 Poster_Goodreau.pdf