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 HC
Q with or without AZ were overall sicker on presentation and had multiple other risk factors including much higher risk based on ethnicity; patients receiving HC
Q 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 HC
Q was associated with a significant survival benefit in a larger cohort of patients from New York City as reported by Mikami et al .
death, ↑35.0%, p=0.31
death, ↑8.0%, p=0.79