Via the estimable Dick Puddlecote comes the report on this piece of research:
Safety evaluation and risk assessment of electronic cigarettes as tobacco cigarette substitutes: a systematic review
The authors look at 97 studies examining the health impacts of vaping. And what do they find:
Currently available evidence indicates that electronic cigarettes are by far a less harmful alternative to smoking and significant health benefits are expected in smokers who switch from tobacco to electronic cigarettes. Research will help make electronic cigarettes more effective as smoking substitutes and will better define and further reduce residual risks from use to as low as possible, by establishing appropriate quality control and standards.
Note that folks - "significant health benefits are expected in smokers who switch". We should be encouraging these things not trying to ban them or ban their promotion.