Introduction:
The role of electronic nicotine delivery systems (ENDS) use on smoking behaviours among adolescents remains controversial. It has been hypothesized that it could constitute a gateway to cigarettes smoking or, rather, a harm reduction alternative protecting from regular smoking. Many studies focusing on adolescents have investigated the role of ENDS on tobacco smoking initiation but very few assessed the role of ENDS on the transition to daily smoking.

Methods:
Using the French 2017 ESCAPAD survey, a nationally representative survey of French teenagers (n= 39,115), we estimated the association between ENDS ever use (=exposed group) and the transition to daily smoking by reaching 17, among ever users of tobacco. Descriptive analyses and Poisson regressions with robust variance and propensity score weighting to deal with confounding were undertaken.

Results:
Among ever smokers (n= 21, 401), adolescents who had experimented ENDS were less likely to have transitioned to daily smoking at 17 (PR = 0.65 [0.63 – 0.68]). They were 32.1 % to have become daily smokers in the exposed group (ENDS ever use) vs 49.6 % in the unexposed group (no ENDS ever use). Most dual ever users started by trying tobacco smoking (71.4 %).

Conclusions:
At this stage, those results do not suggest that vaping intervene into the transition to daily smoking in France. This might be specific to the French context, where smoking remains highly popular among adolescents (25.1 % of daily smokers at 17). As our studied population only concerns 17 years old, those analyses will have to be carried on among older populations to be confirmed.