PROJECT SUMMARY People who inject drugs (PWIDs) are highly vulnerable to contracting SARS-CoV-2 and to the effects of the disease caused by SARS-CoV-2, coronavirus disease 2019 (COVID-19). PWIDs experience underlying medical conditions and unstable housing that put them at increased risk for COVID-19 morbidity and mortality. PWIDs also experience barriers such as a history of stigmatization and discrimination by health care systems and exposure to misinformation that reduces access to health care services, such as SARS-CoV-2 testing and vaccination. The proposed project builds on our Phase I Rapid Acceleration of Diagnostics project (#67; PI: Stormshak) that successfully embedded SARS-CoV-2 testing into syringe exchange programs (SEPs) across the state of Oregon, in collaboration with HIV Alliance (HIVA). The testing program’s success is linked to a contingency management (CM) intervention that increased the rates of testing utilization from 4% to 24% (d = 1.36), even as nationwide testing utilization was decreasing. The first aim of the proposed project is to test the sustained effectiveness of CM on testing outcomes, given the current context of increasing COVID-19 vaccine accessibility. Testing remains critical to prevent the transmission of SARS-CoV-2 among PWIDs who continue to be at high exposure risk, and for whom vaccine hesitancy is high. We will also leverage our partnership with HIVA to establish a COVID-19 vaccine program at HIVA’s SEPs. The second aim is to conduct a randomized control trial (RCT) to examine whether a brief motivational enhancement (ME) intervention (i.e., Connect2Test) augments the effects of CM on SARS-CoV-2 testing and vaccination uptake. Our Phase I study demonstrates that CM improves SARS-CoV-2 testing utilization. CM is also known to increase immunization rates against other infectious diseases, such as Hepatitis B. Additionally, consistent with research showing that ME enhances the effects of CM on health behavior outcomes, we anticipate that Connect2Test will augment CM’s effects on testing and vaccination among PWIDs. Moreover, because ME elicits and strengthens motivation for long-term behavior change, whereas CM prompts immediate and short-term behavior change, we anticipate that CM + ME, versus CM alone, will have long-term effects on SARS-CoV-2 testing, evidenced by participation in repeated testing over time. The third aim of the proposed project is to assess CM and Connect2Test implementation, including a cost-effectiveness analysis of CM alone versus CM plus Connect2Test, to improve long-term sustainability of testing, vaccination, and intervention approaches to mitigate the spread of SARS-CoV-2.