Smoking is Associated with Reduced Frequency of SARS-CoV-2 Infection

Smoking has been described as a risk factor for severe COVID-19. While there is clear evidence that smoking depresses pulmonary immune function and increases the risk for respiratory infectious diseases with severe complications, recent data suggest that it also may have a protective effect from SARS-CoV-2 infection. We therefore investigated the independent impact of smoking on SARS-CoV-2 infection in two separate studies including a representative cohort study (N=988) and a COVID-19 cluster-outbreak (N=404). Cigarette consumption of >=10 cigarettes/day we observed a reduced risk of SARS-CoV-2-infection (fully adjusted OR 0.424 (95% confidence interval 0.253- 0.712). Trial Registration Number: German Clinical Trials Register (https://www.drks.de, ID: DRKS00021306) Funding: Both cohort studies were funded by the Ministry of Labor, Health, and Social Affairs of the State of North Rhine-Westphalia, Germany. Conflict of Interest: All authors declare no conflicts of interest. Ethical Approval: The study was approved by the ethics committee of the medical faculty of University Bonn (approval number 085/20).