Reply to Chan et al.

We agree that smoking might be a risk factor for the severity of COVID-19, but in our previous study, smoking was not so robust compared with our conclusion. Also, we strongly agreed that COVID-19 patients with diabetes or other chronic diseases might worsen the situation of the disease. But these factors were out of the scope of our study and we had published other research on this topic related to diabetes. Because of the limited sample size and original medical records, our study could not cover many factors. But we wish our study will be a useful and meaningful pilot study for future studies.