The authors identified 19 peer-reviewed papers (16 from China, 1 from Korea, and 2 from U.S.) published before April 28, 2020 on COVID-19 patients with data on smoking behavior. The analysis consisted of 11,590 COVID-19 patients, 731 (6.3%) with a history of smoking. Among the patients with a history of smoking, 29.8% experienced COVID-19 progression, compared to 17.6% non-smoking patients who experienced disease progression (OR 1.91, 95% CI 1.42-2.59). *"There was moderate heterogeneity among the studies (I2=38%, p=.048) and no significant evidence of publication bias (Harbord’s p=.813, Peters’ p=.941)."