The author of a related editorial states that this study is one more piece of evidence to suggest that e-cigarettes harm non-smokers and result in a net harm to society and public health, as their use in adolescents and young adults may lead to smoking.
A recent report by Public Health England examined the evidence of the implications of e-cigarettes for public health. It estimates that they are 95% less harmful than cigarettes and may be contributing to falling smoking rates, and finds that there is no evidence they act as a route into smoking for children and non-smokers.
There has however been controversy surrounding the PHE report. For example an editorial in the Lancet (see link below) discusses the paper from which the '95% less harmful' statistic was derived, and the caveats to this research, which the authors comment is an 'extraordinarily flimsy foundation' upon which the report's major conclusion and messages were based. In addition there is a potential conflict of interest associated with the study, as one of the authors served as a consultant to an e-cigarette distributor.