Some studies have reported higher expression of angiotensin-converting enzyme 2 (ACE-2), which is the main receptor of SARS-CoV-2, in the lower respiratory airways of current smokers and COPD patients compared to nonsmokers, and stated that smoking and COPD could contribute to a higher COVID-19 incidence and relatively poorer outcomes [19, 20]. This evidence concerns the gene ACE2 and COVID-19.