Are Individuals with Substance Use Disorders at Higher Risk of SARS-CoV-2 Infection? Population-Based Registry Study in Northern Italy

Background and Aim: This study assesses whether individuals with substance use disorder are at greater risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection than people in the general population. Methods: A population-based study was conducted including 3,780 individuals, diagnosed with alcohol or other drug dependence and cared for by the addiction service (AS) in the province of Reggio Emilia. Standardised incidence ratios (SIRs) and relative 95% confidence intervals (CIs) of being tested and of being SARS-CoV-2 positive in the population of interest compared with those in the general population of Reggio Emilia were calculated. Results: Both individuals with alcohol and those with other drug use disorders had a lower risk of being SARS-CoV-2 positive (SIR = 0.69; 95% CI 0.32–1.30, SIR = 0.56; 95% CI 0.24–1.10, respectively), despite higher rates of being tested than the general population (SIR = 1.48; 95% CI 1.14–1.89, SIR = 1.51; 95% CI 1.20–1.86, respectively). Among HIV-negative persons, 12.5% were positive to SARS-CoV-2, while none was positive among HIV-positive persons. HCV-infected AS clients had a higher risk of both being tested for SARS-CoV-2 (SIR = 1.99; 95% CI 1.26–2.98) and of resulting positive (SIR = 1.53; 95% CI 0.50–3.58). Conclusions: Individuals with alcohol and/or other drug use disorders are at higher risk of being tested for SARS-CoV-2 infection but at lower risk of resulting positive than the general population. Further research is warranted in order to support our findings and to address plausible factors underpinning such associations.