I have used vaping for the past year and have noticed positive improvement in my own health however personal experience is anecdotal and doesnt provide the evidence we want for evidence based medicine. What i can tell you is that there has been no legitimate evidence to indicate that the inhalation of glycerin based nicotine products presents anymore harm than cigarette smoking and most studies point to the vaping of e-liquid to be less harmful than the combustion of tobacco. Vaping is absolutely safer in one specific way in that no Carbon Monoxide can be produced (combustion of a carbon based substance is what creates CO and vaping does not create combustion). I think it is very important in the medical community for us to think of vaping as less bad as opposed to good. the FDA does not allow Electronic cigarettes to be marketed for smoking cessation but that does not mean they cannot be used for harm reduction. As far as recommending them to patients i would opt for encouraging them to quit smoking all together but if they insist on continuing it would be worth a suggestion to minimize some of their risk. as fare as white papers indicating harm reductions take a look at this study https://www.gov.uk/government/publications/e-cigarettes-an-evidence-update