Strengths and Limitations
The strengths of this work include the large sample size and the randomized assignment of participants to each group. It should be noted that these results are intended as a case study of US adults who use e-cigarettes 5 or more days per week; results may not be generalizable to other populations within or outside of the United States. Additionally, in previous VAPER Study waves, all participants received conditional incentives; it is possible that the transition from conditional to hybrid incentives may have influenced survey initiations and completions.