| Study | Reason for exclusion |
|---|---|
| Adkison 2013 | Although this study uses a prospective cohort design, no data on EC use were collected at baseline, with EC use data only being available at follow‐up |
| Al‐Delaimy 2015 | Observational study with no intervention provided ‐ included in previous versions, but excluded from 2020 |
| Anonymous 2019 | Commentary of included study (not primary study) |
| Battista 2013 | Short‐term EC use only |
| Bianco 2019 | Ineligible intervention |
| Biener 2015 | Cohort study, but EC use evaluated retrospectively only |
| Biondi‐Zoccai 2019 | Less than 1 week follow‐up |
| Biondi‐Zoccai 2020 | Acute EC use only |
| Borderud 2014 | Observational study with no EC intervention provided ‐ included in previous versions, but excluded from 2020 |
| Brose 2015 | Observational study with no EC intervention provided ‐ included in previous versions, but excluded from 2020 |
| Brown 2014a | Cross‐sectional survey |
| Bullen 2010 | Short‐term EC use only |
| Bullen 2018 | Withdrawn trial registry |
| Caponnetto 2019 | Ineligible intervention |
| Cavarretta 2019 | Less than 1 week follow‐up |
| Chaumont 2018 | Less than 1 week follow‐up |
| Chaumont 2019 | Ineligible intervention |
| Chausse 2015 | Ineligible study design |
| Choi 2014 | Observational study with no EC intervention provided ‐ included in previous versions, but excluded from 2020 |
| Chorti 2012 | Short‐term EC use only |
| Collins 2019 | Ineligible intervention |
| Cook 2019 | Commentary of included study (not primary study) |
| Cox 2019a | Short‐term abstinence only (< 6 months) |
| Czogala 2012 | Short‐term EC use only |
| D'Ruiz 2017 | Less than 1 week follow‐up |
| Dawkins 2012 | Short‐term EC use only |
| Dawkins 2013a | Short‐term EC use only |
| Dawkins 2014 | Short‐term EC use only |
| Douptcheva 2013 | Longitudinal study, but no data are reported for smoking cessation or reduction or for adverse events |
| Dutra 2014 | Cross‐sectional survey |
| Eissenberg 2010 | Short‐term EC use only |
| Etter 2014 | Observational study with no EC intervention provided ‐ included in previous versions, but excluded from 2020 |
| Farsalinos 2012 | Short‐term EC use only |
| Farsalinos 2013a | Included people that had already stopped smoking conventional cigarettes |
| Farsalinos 2013b | Short‐term EC use only |
| Farsalinos 2013c | Short‐term EC use only |
| Farsalinos 2013d | Short‐term EC use only |
| Flouris 2012 | Short‐term EC use only |
| Flouris 2013 | Short‐term EC use only |
| Gmel 2016 | Cohort study, but EC use only evaluated retrospectively |
| Gottlieb 2019 | Commentary of included study (not primary study) |
| Grana 2014b | Observational study with no EC intervention provided ‐ included in previous versions, but excluded from 2020 |
| James 2016 | Follow‐up at 12 weeks, AE data not collected |
| Kasza 2013 | Longitudinal study, but no data are reported for smoking cessation or reduction or for adverse events |
| Kouretas 2012 | Short‐term EC use only |
| Kousta 2019 | Commentary of included study (not primary study) |
| Lechner 2015 | Less than 1 week follow‐up |
| Lee 2014 | Cross‐sectional survey |
| Manzoli 2015 | Observational study with no EC intervention provided ‐ included in previous versions, but excluded from 2020 |
| Marini 2014 | Short‐term EC use only |
| Mayor 2019 | Commentary of included study (not primary study) |
| Miura 2015 | Tests a device which is not an EC |
| NCT02487953 | Withdrawn trial registry |
| NCT02527980 | No intervention: observation only |
| NCT03036644 | Less than 1 week follow‐up |
| NCT03575468 | Ineligible intervention |
| NCT04107779 | Less than 1 week follow‐up |
| Nolan 2016 | Short‐term abstinence only (< 6 months) |
| NTR6224 | Study terminated early; no usable results. Previously listed as ongoing |
| Palamidas 2014 | Short‐term EC use only |
| Pearson 2012 | Longitudinal study, but no data are reported for smoking cessation or reduction or for adverse events |
| Pokhrel 2013 | Cross‐sectional survey |
| Polosa 2014a | Observational study with no EC intervention provided ‐ included in previous versions, but excluded from 2020 |
| Popova 2013 | Cross‐sectional survey |
| Prochaska 2014 | RCT but no EC intervention provided ‐ included in previous versions, but excluded from 2020 |
| Russo 2018 | Ineligible study design |
| Schober 2014 | Short‐term EC use only |
| Siegel 2011 | Retrospective survey of 222 EC users that responded to a survey sent to 5000 new users of the 'Blu' EC. Likely to be a self‐selected sample |
| Song 2020 | Ineligible patient population |
| St.Helen 2020 | Ineligible intervention |
| Stein 2019 | Commentary of included study (not primary study) |
| Stower 2019 | Ineligible study design |
| Tsikrika 2014 | Short‐term EC use only |
| Tucker 2018 | Short‐term abstinence only (< 6 months) |
| Tzatzarakis 2013 | Short‐term EC use only |
| Vakali 2014 | Short‐term EC use only |
| Valentine 2016 | Less than 1 week follow‐up |
| Van Heel 2017 | Ineligible study design |
| Vansickel 2010 | Short‐term EC use only |
| Vansickel 2012 | Short‐term EC use only |
| Vansickel 2013 | Short‐term EC use only |
| Vardavas 2012 | Short‐term EC use only |
| Vickerman 2013 | Cross‐sectional survey |
| Voos 2019 | Less than 1 week follow‐up |
| Voos 2020 | Ineligible study design |
| Wagener 2014 | EC use for up to 1 week, but does not report on any adverse events |
| Walele 2016a | RCT but follow‐up too short |
| Walele 2016b | RCT but follow‐up too short |
| Yan 2015 | Ineligible study design |
| Yuki 2017 | Less than 1 week follow‐up |
| Zhang 2019 | Commentary of included study (not primary study) |
EC: electronic cigarette