IntroductionThe objective of this systematic review was to identify, report and critically appraise studies that have reported health outcomes from use of ENDS.MethodsWe conducted a systematic review of all published literature on the health impact of ENDS products from 1st January 2015 until February 1, 2020, following the PRISMA protocol, including across the databases, PubMed, Embase, Scopus and Google Scholar. Medical subject headings were used in the execution of PubMed searches.A category for the level of evidence was assigned blindly using the Centres for Evidence Based Medicine framework. A similar approach was adopted to evaluate methodological quality of each study utilizing the National Institutes for Health (NIH) Quality Assessment Tools.ResultsThe database search identified 755 studies and a further 265 were identified from other sources and reference reviews of which 37 studies met the eligibility criteria.The majority of studies were of low strength for levels of evidence including 24 (65%) cross-sectional, 1(2.7%) case-control and six (16%) case studies. There were four (11%) cohort studies and only one (2.7%) RCT. There was only one (2.7%) meta-analysis or pooled study of observational study designs; there were no pooled results of randomized controlled trials. Of 37 studies, eight (22%) studies reported on benefits, two (2%) studies were neutral, reporting on both harm and benefits, the remaining 27 (73%) reported only on harms. The quality ratings were poor (20, 54%), fair (9, 24%) and good (8, 22%).In our review ENDS use has not been shown to be causative for any CVD outcomes and has been shown to …