Abstract
The recent rise in HIV incidence among people who inject drugs in the United States highlights an urgent need to improve HIV testing, treatment linkage, and pre-exposure prophylaxis access in this group. Syringe services programs (SSPs) play a critical role by offering or linking clients to these services, yet little is known about how such care is delivered. Informed by the Consolidated Framework for Implementation Research, we conducted qualitative interviews with 41 representatives from 27 SSPs across the United States to characterize the current service delivery landscape, identify barriers to care, and explore modifiable implementation determinants. Rapid qualitative analysis revealed four primary HIV service delivery models: "one-stop shop" offering integrated, on-site HIV testing and follow-up care provided by the SSP; "test and refer" with integrated, on-site testing services followed by referrals to external partners for follow-up care; "co-located services" with SSPs relying on external partner organizations to provide HIV testing (and additional services) on-site; and "hand-off" involving referrals to off-site, external partners for HIV testing and follow-up care. SSPs faced varied implementation challenges, including staffing, funding, and space constraints; competing priorities; availability and accessibility of local partnerships; as well as SSP culture, which values participant autonomy (recipient-centeredness). These contextual factors influenced the feasibility and acceptability of HIV services and why SSPs adopted a particular service delivery model. To strengthen HIV prevention and care in SSPs, tailored implementation strategies are needed that account for programs' unique constraints and capacities.