Search methods: We searched the Cochrane Tobacco Addiction Group Specialized Register until February 1, 2023, and the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO until July 1, 2023, and checked references and contacted study authors.
Selection criteria: We included trials in which smokers were randomized to an EC or a control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention, as these studies have the potential to provide additional information on harms and longer-term use. Studies had to report an eligible outcome.
Main Results: We included 88 completed studies (10 new in this update), representing 27,235 participants, of which 47 were randomized controlled trials (RCTs). Of the included studies, 10 (all but one contributed to the main comparisons) were rated as low risk of bias overall, 58 as high risk overall (including all nonrandomized studies), and the remainder as uncertain risk. There is high certainty that nicotine-containing ECs increase quit rates compared with nicotine replacement therapy. There is evidence of moderate certainty, limited by imprecision, that EC with nicotine increases quit rates compared with EC without nicotine.
