ABSTRACT
Background: People who inject drugs (PWID) are vulnerable to SARS-CoV-2 and severe disease but have low rates of COVID-19 testing and vaccination due to multilevel barriers. We partnered with a mobile syringe service program (SSP) in San Diego County, CA, to develop the theory-informed LinkUP intervention to increase COVID-19 testing and vaccination among PWID. Method(s): From March-June 2022, we conducted a pilot randomized controlled trial (RCT;ClinicalTrials.gov #NCT05181657) to assess efficacy of LinkUP vs. a didactic attention-matched control condition in increasing COVID-19 testing uptake and acceptance of vaccination referrals. Based on Social Cognitive Theory, trained, SSP-hired peer counsellors delivered tailored education, motivational interviewing, and problem-solving and planning to the active LinkUP intervention arm. We referred eligible participants (PWID, >=18 years old, San Diego County residents without recent voluntary COVID-19 testing or fully vaccinated status) to mobile SSP sites that had been randomized by week to offer LinkUP or the control condition;all participants were then offered on-site rapid COVID-19 antigen testing and vaccination referrals. Our intent-to-treat analysis used Chi-square tests to compare intervention groups' outcomes and log-binomial regression to estimate preliminary intervention efficacy and explore potential moderation. Result(s): Among 150 participants, median age was 41 years, 33% identified as Latinx and 65% as male, 73% were experiencing homelessness, and 45% had prior mandatory COVID-19 testing. Overall, we only detected one SARS-CoV-2 case. However, more active intervention vs. control participants agreed to COVID-19 testing (77.3% vs. 22.7%;p< .001) and vaccine referrals (32.4% vs. 13.3%;p=0.006). Homelessness moderated intervention effects: LinkUP increased COVID-19 testing uptake more among participants experiencing homelessness (adjusted risk ratio [aRR]: 1.64;95% CI: 1.27-2.12) than those not experiencing homelessness (aRR: 1.25;95% CI: 0.99-1.56). Conclusion(s): Findings from this RCT support the efficacy of LinkUP in increasing COVID-19 testing and acceptance of vaccination referrals among PWID presenting at mobile SSP sites, particularly for those experiencing homelessness. This research underscores the significance of communityacademic partnerships when working with PWID and identifies a promising model that could be adapted to increase access to other underutilized vaccines in this vulnerable population.