E-liquid flavors and nicotine concentration choices over 6 months after a smoking cessation attempt with ENDS: Secondary analyses of a randomized controlled trial.

Introduction
Many tobacco smokers try to quit with electronic nicotine delivery systems (ENDS or e-cigarettes). We aimed to describe e-liquid flavors and nicotine concentration use over 6 months in a prospective cohort of smokers willing to quit with ENDS.Methods
We included 622 participants from the intervention group of the Efficacy, Safety and Toxicology of ENDS randomized controlled trial. Participants were adult smokers smoking at least five cigarettes a day. They received free ENDS and a choice of 6 e-liquid flavors in 4 nicotine concentrations and smoking cessation counseling. We tracked flavor choice and nicotine concentration at 1, 2, 4, and 8 weeks, and at 6 months, after the target quit date, comparing participants who reported only vaping (exclusive e-cigarette users) to those who vaped and smoked (dual users) over the last 7 days. We applied multivariable regression models to compute adjusted risk ratios (ARR).Results
At Week 1, 66% (n=409) were exclusive e-cigarette users, and 21% (n=129) were dual users. At Month 6, 43% (n=266) were exclusive e-cigarette users, and 16% (n=102) were dual users. While flavor choices were similar at Week 1, at 6 months, exclusive e-cigarette users reported using more fruity flavors than dual users (31% vs 22%, ARR=2.10; 95% CI: 1.21-3.66). The nicotine concentration used initially was similar in both groups and diminished over time. At 6 months, exclusive e-cigarette users used a lower mean nicotine concentration than dual users (6.3 vs 8.2 mg/mL, difference= -1.55; 95% CI: -2.84 - -0.25 mg/mL).Conclusions
After 6 months, exclusive e-cigarette users used more fruity-flavored e-liquids and chose a lower mean nicotine concentration than dual users.