Limitations for this study may include missing data for some confounding variables as well as the potential for inaccuracies in electronic health records, such as lack of documentation of smoking and pre-existing conditions for some patients. The single-center design of this study may limit the generalizability of these results. As the study is observational, its results should not be taken to reveal a definite benefit or harm of HCQ treatment, although results do not support usage of HCQ to treat COVID-19 at this time.