As ever...the original article is more useful.... http://journals.plos.org...371/journal.pone.0116861 Not behind a paywall as its on PLOS. 'In summary, this study reports a murine model of E-cig exposure and demonstrates that E-cig exposure elicits impaired pulmonary anti-microbial defenses. Hence, E-cig exposure as an alternative to cigarette smoking must be rigorously tested in users for their effects on immune response and susceptibility to bacterial and viral infections.' The study was not trying to compare e-cigs with normal cigs. JotBW - I think are trying to criticise the study based on the newspaper article rather than its actual intention. Further to that, there WAS a control group of mice only being exposed to air. For fullness of information, they have also used a 'comparator' - serum cotinine (a metabolite of nicotine), and deemed that the levels in the mice were similar to those found in human users after exposure to e-cig vapour. They acknowledge a number of limitations to the study within the discussion section, including the use of this as an indicator. They end with: 'Despite the common perception that E-cigs are safe, this study clearly demonstrates that E-cig use, even for relatively brief periods, may have significant consequences to respiratory health in an animal model; and hence, E-cigs need to be tested more rigorously, especially in susceptible populations.' One of their references, http://www.karger.com/Article/FullText/353253 , sums up why e-cigs have not yet been deemed safe or effective for use for smoking cessation.