Preliminary Efficacy of a Theory-Informed Intervention to Increase COVID-19 Testing Uptake Among People Who Inject Drugs in San Diego County: Findings From a Pilot Randomized Controlled Trial

BACKGROUND: People who inject drugs (PWID) have low rates of COVID-19 testing yet are vulnerable to severe disease. In partnership with a mobile syringe service program (SSP) in San Diego County, CA, we developed the evidence-, community-, and Social Cognitive Theory-informed “LinkUP” intervention (tailored education, motivational interviewing, problem-solving, and planning) to increase COVID-19 testing uptake among PWID. PURPOSE: To assess preliminary efficacy of LinkUP in increasing PWID COVID-19 testing in a pilot randomized controlled trial (RCT). METHODS: We referred participants (PWID, ≥18 years old, San Diego County residents who had not recently undergone voluntary COVID-19 testing) to mobile SSP sites that had been randomized (by week) to offer the active LinkUP intervention or didactic attention-control conditions delivered by trained peer counselors. Following either condition, counselors offered on-site rapid COVID-19 antigen testing. Analyses estimated preliminary intervention efficacy and explored potential moderation. RESULTS: Among 150 participants, median age was 40.5 years, 33.3% identified as Hispanic/Latinx, 64.7% were male, 73.3% were experiencing homelessness, and 44.7% had prior mandatory COVID-19 testing. The LinkUP intervention was significantly associated with higher COVID-19 testing uptake (p < .0001). Homelessness moderated intervention effects; LinkUP increased COVID-19 testing uptake more among participants experiencing homelessness (adjusted risk ratio [aRR]: 1.80; 95% CI: 1.56–2.09; p < .0001) than those not experiencing homelessness (aRR: 1.20; 95% CI: 1.01–1.43; p = .04). CONCLUSIONS: Findings from this pilot RCT support the preliminary efficacy of the “LinkUP” intervention to increase COVID-19 testing among PWID and underscore the importance of academic-community partnerships and prevention service delivery through SSPs and other community-based organizations serving vulnerable populations.