Retrospective 3,817 chronic HCQ patients showing 4.4% COVID-19 positive rate, 1.3% severe. There is no comparison with a control group. Authors note that there was a 3.6% incidence among 2,032,863 patients in one of the regions (Castilla La Mancha), however they provide no information on this group - it is expected that the mostly systemic autoimmune disease patients in the treatment group are older on average. Additonally, other research shows that the risk of COVID-19 for systemic autoimmune disease patients is much higher overall, Ferri et al. show OR 4.42, p
Cifuentes et al., 1/23/2021, peer-reviewed, 18 authors.