Cigarette Smoking and Risk of SARS-CoV-2 infection and Disease Severity Among Adults in an Integrated Health Care System in California.

In this cohort study of 2.4 million adults, adjusting for socio-demographics and medical comorbidities, current cigarette smoking was associated with a lower risk of both COVID-19 infection and severe COVID-19 illness compared to never-smoking. A history of smoking was associated with a slightly lower risk of COVID-19 infection and a modestly higher risk of severe COVID-19 illness compared to never-smoking. The lower observed COVID-19 risk for current versus never-smoking deserves further investigation. Results support prioritizing individuals with smoking-related comorbidities for vaccine outreach and treatments as they become available.