Assessing E-Cigarettes for Tobacco Harm Reduction in the Context of Lung Cancer Screening

Inclusion Criteria: * Participants who completed the Screen Assist study (NCT03611881) and self-reported smoking cigarettes at the end of the study were asked to complete a survey to ascertain their potential interest in participating in a research study to test the effects of switching from combustible cigarettes (CC) to electronic cigarettes (EC). Individuals who expressed interest in switching to EC on that survey were screened for eligibility for this pilot study * Smoked ≥5 cigarettes/day in past month * Smoking status at study entry confirmed by breath carbon monoxide (CO) ≥ 6ppm * Willing to try switching from CC to EC for 4 weeks * Owns a mobile telephone * English speaking * Willing to travel to the Massachusetts General Hospital campus for 3 in-person visits. Exclusion Criteria: * Plans to quit smoking and has set a quit date in the next 30 days * Used smoking cessation treatment in the past 30 days * Used EC on \>2 days in the past 30 days * Hospitalized for acute coronary syndrome, unstable angina, congestive heart failure, stroke, pneumonia or chronic pulmonary disease/asthma exacerbation in the past 1 month * Not willing to abstain from smoking marijuana in the 24h before each study visit