Susceptibility to COVID-19 in patients treated with antimalarials: a population based study in Emilia-Romagna, Northern Italy.

Objectives To evaluate the susceptibility of coronavirus disease 2019 (COVID-19) in patients with autoimmune conditions treated with antimalarials in a population-based study. Methods All residents treated with chloroquine/hydroxychloroquine (CQ/HCQ) from July through December 2019 and living in 3 provinces of Regione Emilia-Romagna were identified by drug prescription registries and matched with the registry containing all residents, living in the same areas, who have had swabs and positive swabs for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Results 4,408 patients were identified. The prevalence of antimalarial users was 0.85/1000 in males and 3.3/1000 in females. The cumulative incidence of being tested during the study period was 2.7% in the general population and 3.8% in CQ/HCQ users, while the cumulative incidence of testing positive was 0.55% in the general population and 0.70% in users. Multivariate models showed that CQ/HCQ users had a slightly higher probability of being tested compared to general population (OR 1.09, 95%CI 0.94-1.28), the same probability of being diagnosed with COVID-19 (OR 0.94, 95%CI 0.66-1.34), and a slightly lower probability of being positive once tested (OR 0.83, 95%CI 0.56-1.23). All three differences were not statistically significant. Conclusions Our study did not support the prophylactic use of antimalarials for COVID-19.