Modeling the joint effects (or combined effects) of adolescent and adult PrEP for sexual minority males in the US

Modeling the joint effects (or combined effects) of adolescent and adult PrEP for sexual minority males in the US

Abstract Accepted: National HIV Conference in March 2019 (Atlanta, GA) and Sunbelt Directors Meeting in July 2019 (Montreal, Quebec). 

Background: HIV pre-exposure prophylaxis (PrEP) is an effective and safe intervention approved for use by adults and adolescents. Previous modeling studies have evaluated the potential impact of PrEP interventions on the HIV epidemic among adult men who have sex with men (MSM) and adolescent sexual minority males (ASMM) with results indicating that a significant number of infections could be averted within each population. However, the sexual networks comprising these two populations are not distinct. There are inherent dependencies between these populations which are not captured in age-bounded simulations which may be important for the evaluation of the impact of PrEP on the HIV epidemic. This project evaluates the potential impact of PrEP interventions among both adult MSM and ASMM and highlights the impact of including inter-population network dynamics.   

Methods: An agent-based network transmission model was built using the EpiModel platform, which relies on the statnet suite of modeling tools. The networks were estimated using separable temporal exponential random graphs models (STERGMs). From the epidemic simulation, we estimated the number of HIV infections averted, the percent of infections averted (PIA), and changes in incidence and prevalence for a population of 13-39-year-old MSM. PrEP was implemented among adult MSM age 19-39 following CDC guidelines, which rely in part on network conditions (e.g., known positive main partner, multiple partners of unknown status). A program of PrEP implementation among sexually active 16-18 year-old ASMM was then added to the adult-focused program. 

Results: The implementation of a PrEP program for adult MSM following CDC guidelines with 40% coverage resulted in 29.0% (95% Credible Interval (CrI): 24.0%, 34.4%) of infections being averted among all MSM (adult and ASMM) over 10 years, reducing prevalence from 23.2% (95% CrI: 21.4%, 24.5%) to 17.0% (95% CrI: 15.7%, 18.0%). For ASMM specifically, the adult-focused PrEP program reduced mean prevalence from 6.0% (95% CrI: 4.0%, 8.3%) to 4.3% (95% CrI: 2.3%, 6.5%). The addition of a PrEP program targeting 16-18 year old ASMM with 30% coverage increased the PIA to 29.9% (23.6%, 35.0%) among all MSM and further reduced prevalence among ASMM to 3.8% (95% CrI: 2.0%, 6.0%). 

Conclusion: Our model that considers integrated networks across age boundaries confirms many of the findings from previous analyses that used age-restricted populations while also introducing several new insights. For example, we find that PrEP use among only adult MSM may have as large or even a larger impact on HIV incidence among ASMM than a PrEP intervention specifically targeting ASMM. We discuss the urgent need for more network data for adolescent ASMM, despite the challenges in obtaining it. 

Downloadable Files:
FY5_2018 NHPC_Hamilton.PPTX