Inclusion Criteria:

• ≥ 18 years and ≤ 65 years of age.
• No use of tobacco in any form (except E-cigarettes) in the past 3 months.
• Expired air carbon monoxide < 8 ppm.
• Used at least 1 disposable e-cigarette or 1 refillable unit (tank, cartomizer, pod) per week for the past 3 months.
• Motivated to stop using e-cigarettes.
• Able to participate fully in all aspects of the study.
• Understand and sign the study informed consent.
• Subject is in good health as determined by the clinical investigators.

Exclusion Criteria: 

• Current moderate or severe depression as assessed by a score of ≥ 16 on the Center for Epidemiologic Studies-Depression (CES-D).
• A lifetime history of psychosis, bipolar disorder or schizophrenia.
• Use of anti-psychotic medication within the past 30 days;
• Use of any treatments for tobacco dependence within the past 30 days.
• Use of an investigational drug within the past 30 days.
• Recent history (past 3 months) of abuse of, or dependence on, a substance other than nicotine including: heavy alcohol consumption (If male, drinking > 14 alcoholic beverages per week for the past month and if female, drinking > 7 alcoholic beverages per week for past month); use of cocaine, heroin, club drugs (i.e., MDMA/“ecstasy”); methamphetamine, or hallucinogens (e.g., LSD) at any time during the past 3 months; and use of marijuana CBD) on a weekly basis for the past 3 months.
• Women who are pregnant or lactating, or who are of childbearing potential and are likely to become pregnant during the medication phase, or a male who is able to father a child, and are not willing to use a reliable form of contraception, will also be excluded (reliable forms of contraception include oral contraception, diaphragm, condom (with spermicide), injections, intrauterine device, surgical sterilization, and abstinence).
• Subject describes having a medical history of:
  • unstable angina;
  • myocardial infarction within the past 3 months; 
  • coronary angioplasty; or 
  • an untreated cardiac dysrhythmia.
• Subject currently has cancer [excluding non-melanoma skin cancer] not in remission.
• Known allergy to varenicline.
• Subject has a medical condition deemed by the investigators to be exclusionary to the study.