Restrospective observational late stage study showing no significant differences but calling for clinical trials.
Zervos et al.  point out serious limitations that they say should be corrected on the record: patients receiving HCQ with or without AZ were overall sicker on presentation and had multiple other risk factors including much higher risk based on ethnicity; patients receiving HCQ were more likely to be obese, diabetic, have chronic lung disease, and cardiovascular conditions; yet these sicker patients had approximately the same mortality rates compared to patients with a milder course of the disease and less risk factors. However, the authors conclude that "there are no significant benefits." It is noteworthy that HCQ was associated with a significant survival benefit in a larger cohort of patients from New York City as reported by Mikami et al .
See also .
Rosenberg et al., 5/11/2020, retrospective, USA, North America, peer-reviewed, 14 authors.
risk of death, 35.0% higher, RR 1.35, p = 0.31, treatment 189 of 735 (25.7%), control 28 of 221 (12.7%), adjusted per study.
risk of death, 8.0% higher, RR 1.08, p = 0.79, treatment 54 of 271 (19.9%), control 28 of 221 (12.7%), adjusted per study.