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Meta-Analysis
. 2020 Oct 14;10(10):CD010216.
doi: 10.1002/14651858.CD010216.pub4.

Electronic cigarettes for smoking cessation

Jamie Hartmann-Boyce  1 , Hayden McRobbie  2 , Nicola Lindson  1 , Chris Bullen  3 , Rachna Begh  1 , Annika Theodoulou  1 , Caitlin Notley  4 , Nancy A Rigotti  5 , Tari Turner  6 , Ailsa R Butler  1 , Peter Hajek  7
Affiliations
Meta-Analysis

Electronic cigarettes for smoking cessation

Jamie Hartmann-Boyce et al. Cochrane Database Syst Rev. .

Update in

Abstract

Background: Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol formed by heating an e-liquid. People who smoke report using ECs to stop or reduce smoking, but some organisations, advocacy groups and policymakers have discouraged this, citing lack of evidence of efficacy and safety. People who smoke, healthcare providers and regulators want to know if ECs can help people quit and if they are safe to use for this purpose. This review is an update of a review first published in 2014.

Objectives: To evaluate the effect and safety of using electronic cigarettes (ECs) to help people who smoke achieve long-term smoking abstinence.

Search methods: We searched the Cochrane Tobacco Addiction Group's Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO for relevant records to January 2020, together with reference-checking and contact with study authors.

Selection criteria: We included randomized controlled trials (RCTs) and randomized cross-over trials in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention. To be included, studies had to report abstinence from cigarettes at six months or longer and/or data on adverse events (AEs) or other markers of safety at one week or longer.

Data collection and analysis: We followed standard Cochrane methods for screening and data extraction. Our primary outcome measures were abstinence from smoking after at least six months follow-up, AEs, and serious adverse events (SAEs). Secondary outcomes included changes in carbon monoxide, blood pressure, heart rate, blood oxygen saturation, lung function, and levels of known carcinogens/toxicants. We used a fixed-effect Mantel-Haenszel model to calculate the risk ratio (RR) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data from these studies in meta-analyses.

Main results: We include 50 completed studies, representing 12,430 participants, of which 26 are RCTs. Thirty-five of the 50 included studies are new to this review update. Of the included studies, we rated four (all which contribute to our main comparisons) at low risk of bias overall, 37 at high risk overall (including the 24 non-randomized studies), and the remainder at unclear risk. There was moderate-certainty evidence, limited by imprecision, that quit rates were higher in people randomized to nicotine EC than in those randomized to nicotine replacement therapy (NRT) (risk ratio (RR) 1.69, 95% confidence interval (CI) 1.25 to 2.27; I2 = 0%; 3 studies, 1498 participants). In absolute terms, this might translate to an additional four successful quitters per 100 (95% CI 2 to 8). There was low-certainty evidence (limited by very serious imprecision) of no difference in the rate of adverse events (AEs) (RR 0.98, 95% CI 0.80 to 1.19; I2 = 0%; 2 studies, 485 participants). SAEs occurred rarely, with no evidence that their frequency differed between nicotine EC and NRT, but very serious imprecision led to low certainty in this finding (RR 1.37, 95% CI 0.77 to 2.41: I2 = n/a; 2 studies, 727 participants). There was moderate-certainty evidence, again limited by imprecision, that quit rates were higher in people randomized to nicotine EC than to non-nicotine EC (RR 1.71, 95% CI 1.00 to 2.92; I2 = 0%; 3 studies, 802 participants). In absolute terms, this might again lead to an additional four successful quitters per 100 (95% CI 0 to 12). These trials used EC with relatively low nicotine delivery. There was low-certainty evidence, limited by very serious imprecision, that there was no difference in the rate of AEs between these groups (RR 1.00, 95% CI 0.73 to 1.36; I2 = 0%; 2 studies, 346 participants). There was insufficient evidence to determine whether rates of SAEs differed between groups, due to very serious imprecision (RR 0.25, 95% CI 0.03 to 2.19; I2 = n/a; 4 studies, 494 participants). Compared to behavioural support only/no support, quit rates were higher for participants randomized to nicotine EC (RR 2.50, 95% CI 1.24 to 5.04; I2 = 0%; 4 studies, 2312 participants). In absolute terms this represents an increase of six per 100 (95% CI 1 to 14). However, this finding was very low-certainty, due to issues with imprecision and risk of bias. There was no evidence that the rate of SAEs varied, but some evidence that non-serious AEs were more common in people randomized to nicotine EC (AEs: RR 1.17, 95% CI 1.04 to 1.31; I2 = 28%; 3 studies, 516 participants; SAEs: RR 1.33, 95% CI 0.25 to 6.96; I2 = 17%; 5 studies, 842 participants). Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate over time with continued use. Very few studies reported data on other outcomes or comparisons and hence evidence for these is limited, with confidence intervals often encompassing clinically significant harm and benefit.

Authors' conclusions: There is moderate-certainty evidence that ECs with nicotine increase quit rates compared to ECs without nicotine and compared to NRT. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain. More studies are needed to confirm the degree of effect, particularly when using modern EC products. Confidence intervals were wide for data on AEs, SAEs and other safety markers. Overall incidence of SAEs was low across all study arms. We did not detect any clear evidence of harm from nicotine EC, but longest follow-up was two years and the overall number of studies was small. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates. Further RCTs are underway. To ensure the review continues to provide up-to-date information for decision-makers, this review is now a living systematic review. We will run searches monthly from December 2020, with the review updated as relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

PubMed Disclaimer

Conflict of interest statement

RB holds an NIHR grant, however this did not directly fund this current work. She is principal investigator of an ongoing study listed in this review.

CB was principal investigator on the ASCEND e‐cigarette trial reported in the Cochrane review and a co‐investigator on the ASCEND II trial and several other studies included in the review. CB has provided consultancy for J&J KK (Japan) on NRT products.

ARB's work on this review has been supported by Cancer Research UK Project Award funding. This is not deemed a conflict of interest.

PH provided consultancy for and received research funding from Pfizer, a manufacturer of stop‐smoking medications. He was principal investigator on one of the trials included in this review and co‐investigator on other relevant studies.

JHB has received support for this work from the Cochrane Review Support Programme and the University of Oxford's Returning Carer's Fund. Neither of these are deemed conflicts of interest.

NL has received payment for lectures on systematic review methodology, and has been an applicant on project funding to carry out priority setting and systematic reviews in the area of tobacco control (NIHR funded). None of this is deemed a conflict of interest.

HM has received honoraria for speaking at smoking cessation educational events and sitting on an advisory board organised by Pfizer.

CN has no known conflicts of interest.

NR has received royalties from UpToDate, Inc., for chapters on electronic cigarettes and occasional fees from academic hospitals or professional medical societies for lectures on smoking cessation that include discussion of electronic cigarettes. Dr. Rigotti was an member of the committee that produced the 2018 National Academies of Science, Engineering, and Medicine's Consensus Study Report on the Public Health Benefits of E‐cigarettes. She was unpaid for this work. Outside the topic of e‐cigarettes, Dr. Rigotti has received honoraria from Achieve Life Sciences for consulting about cytisine and travel reimbursement (but no honoraria) from Pfizer for attending advisory boards regarding varenicline.

AT's work on this review has been supported by the Cochrane Review Support Programme and the University of Oxford's Returning Carer's Fund. Neither of these are deemed conflicts of interest.

TT has no known conflicts of interest.

Figures

1
1
2020 Flow diagram
2
2
Study flow diagram for review update 2016
3
3
Study flow diagram for original review, 2014
4
4
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
1.1
1.1. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 1: Smoking cessation
1.2
1.2. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 2: Adverse events
1.3
1.3. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 3: Serious adverse events
1.4
1.4. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 4: Carbon monoxide (ppm)
1.5
1.5. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 5: Heart rate (bpm)
1.6
1.6. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 6: Systolic blood pressure
1.7
1.7. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 7: Blood oxygen saturation
1.8
1.8. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 8: 3‐HPMA (pmol/mg creatinine)
1.9
1.9. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 9: NNAL (pmol/mg creatinine))
1.10
1.10. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 10: 2‐HPMA (pmol/mg creatinine)
1.11
1.11. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 11: HMPMA (pmol/mg creatinine)
1.12
1.12. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 12: PheT (pmol/mg creatinine)
1.13
1.13. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 13: CEMA (pmol/mg creatinine)
1.14
1.14. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 14: AAMA (pmol/mg creatinine)
1.15
1.15. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 15: FEV1 (ml)
1.16
1.16. Analysis
Comparison 1: Nicotine EC versus NRT, Outcome 16: FEV1/FVC (%)
2.1
2.1. Analysis
Comparison 2: Nicotine EC versus varenicline, Outcome 1: Smoking cessation
2.2
2.2. Analysis
Comparison 2: Nicotine EC versus varenicline, Outcome 2: Serious adverse events
3.1
3.1. Analysis
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 1: Smoking cessation
3.2
3.2. Analysis
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 2: Adverse events
3.3
3.3. Analysis
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 3: Serious adverse events
3.4
3.4. Analysis
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 4: Carbon monoxide (ppm)
3.5
3.5. Analysis
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 5: Heart rate
3.6
3.6. Analysis
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 6: Systolic blood pressure
3.7
3.7. Analysis
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 7: FeNO (ppb)
3.8
3.8. Analysis
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 8: FEV1 (l)
3.9
3.9. Analysis
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 9: FVC (l)
3.10
3.10. Analysis
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 10: FEV1/FVC
4.1
4.1. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 1: Smoking cessation
4.2
4.2. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 2: Adverse events
4.3
4.3. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 3: Serious adverse events
4.4
4.4. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 4: Carbon monoxide (ppm)
4.5
4.5. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 5: Heart rate (bpm)
4.6
4.6. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 6: Systolic blood pressure
4.7
4.7. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 7: Blood oxygen saturation
4.8
4.8. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 8: 3‐HPMA (SMD)
4.9
4.9. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 9: NNAL (SMD)
4.10
4.10. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 10: 2‐HPMA (pmol/mg creatinine)
4.11
4.11. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 11: HMPMA (pmol/mg creatinine)
4.12
4.12. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 12: PheT (pmol/mg creatinine)
4.13
4.13. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 13: CEMA (pmol/mg creatinine)
4.14
4.14. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 14: AAMA (pmol/mg creatinine)
4.15
4.15. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 15: S‐PMA (nanograms)
4.16
4.16. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 16: FVC (litres)
4.17
4.17. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 17: FEV1 (litres)
4.18
4.18. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 18: FEF 25‐75 (litres/second))
4.19
4.19. Analysis
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 19: PEF 25‐75 (litres/minute)
5.1
5.1. Analysis
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 1: Smoking cessation
5.2
5.2. Analysis
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 2: Adverse events
5.3
5.3. Analysis
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 3: Serious adverse events
5.4
5.4. Analysis
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 4: Carbon monoxide (ppm)
5.5
5.5. Analysis
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 5: FeNO (ppb)
5.6
5.6. Analysis
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 6: FEV1 (%)
5.7
5.7. Analysis
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 7: FVC (%)
6.1
6.1. Analysis
Comparison 6: Nicotine EC + NRT versus NRT, Outcome 1: Smoking cessation
6.2
6.2. Analysis
Comparison 6: Nicotine EC + NRT versus NRT, Outcome 2: Adverse events
6.3
6.3. Analysis
Comparison 6: Nicotine EC + NRT versus NRT, Outcome 3: Serious adverse events
7.1
7.1. Analysis
Comparison 7: Higher versus lower nicotine content, Outcome 1: Serious adverse events
7.2
7.2. Analysis
Comparison 7: Higher versus lower nicotine content, Outcome 2: Carbon monoxide (ppm)
7.3
7.3. Analysis
Comparison 7: Higher versus lower nicotine content, Outcome 3: Heart rate
7.4
7.4. Analysis
Comparison 7: Higher versus lower nicotine content, Outcome 4: Systolic blood pressure
7.5
7.5. Analysis
Comparison 7: Higher versus lower nicotine content, Outcome 5: FeNO (ppb)
7.6
7.6. Analysis
Comparison 7: Higher versus lower nicotine content, Outcome 6: FEV1 (l)
7.7
7.7. Analysis
Comparison 7: Higher versus lower nicotine content, Outcome 7: FVC (l)
7.8
7.8. Analysis
Comparison 7: Higher versus lower nicotine content, Outcome 8: FEV1/FVC
8.1
8.1. Analysis
Comparison 8: Non‐nicotine EC versus behavioural support only/no support, Outcome 1: Smoking cessation
9.1
9.1. Analysis
Comparison 9: Non‐nicotine EC + NRT versus NRT, Outcome 1: Smoking cessation
9.2
9.2. Analysis
Comparison 9: Non‐nicotine EC + NRT versus NRT, Outcome 2: Adverse events
9.3
9.3. Analysis
Comparison 9: Non‐nicotine EC + NRT versus NRT, Outcome 3: Serious adverse events
10.1
10.1. Analysis
Comparison 10: Non‐nicotine EC versus NRT, Outcome 1: Smoking cessation
10.2
10.2. Analysis
Comparison 10: Non‐nicotine EC versus NRT, Outcome 2: Adverse events
10.3
10.3. Analysis
Comparison 10: Non‐nicotine EC versus NRT, Outcome 3: Serious adverse events
See this image and copyright information in PMC

Update of

Comment in

References

References to studies included in this review

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    1. Kumral TL, Saltürk Z, Yildirim G, Uyar Y, Berkiten G, Atar Y, et al. How does electronic cigarette smoking affect sinonasal symptoms and nasal mucociliary clearance? B-ENT 2016;12(1):17-21. - PubMed
Lee 2018 {published data only}
    1. Lee SM, Tenney R, Wallace A, Arjojmandi M. The end perioperative smoking pilot study: a randomized trial comparing e-cigarettes versus nicotine patch. Canadian Journal of Anesthesia 2017;64(1 Supplement 1):S48-S49.
    1. Lee SM, Tenney R, Wallace AW, Arjomandi M. E-cigarettes versus nicotine patches for perioperative smoking cessation: a pilot randomized trial. PeerJ 2018;6(9):e5609. - PMC - PubMed
    1. NCT02482233. A pilot randomized controlled clinical trial - "Electronic nicotine delivery device (e-cigarette) for perioperative smoking cessation in veterans". clinicaltrials.gov/show/NCT02482233 (accessed 17 February 2016).
Lee 2019 {published data only}
    1. KCT0001277. Effect of an electronic cigarette for smoking reduction and cessation in Korean male smokers: a randomized, controlled study. KCT0001277 2014 (accessed 15 August 2016). - PubMed
    1. Lee SH, Ahn SH, Cheong YS. Effect of electronic cigarettes on smoking reduction and cessation in Korean male smokers: a randomized controlled study. Journal of the American Board of Family Medicine 2019;32(4):567-74. - PubMed
Lucchiari 2020 {published data only}
    1. Lucchiari C, Masiero M, Veronesi G, Maisonneuve P, Spina S, Jemos C, et al. Benefits of e-cigarettes among heavy smokers undergoing a lung cancer screening program: randomized controlled trial protocol. JMIR Research Protocols 2016;5(1):e21. [PMID: ] - PMC - PubMed
    1. NCT02422914. Benefits of tobacco free cigarette among heavy smokers undergoing a lung cancer screening program: a randomized controlled study. clinicaltrials.gov/show/NCT02422914 (accessed 17 February 2016).
Martner 2019 {published data only (unpublished sought but not used)}
    1. Martner SG, Dallery J. Technology-based contingency management and e-cigarettes during the initial weeks of a smoking quit attempt. Journal of Applied Behavior Analysis 2019;52(4):928-43. - PMC - PubMed
McRobbie 2015 {published data only}
    1. McRobbie H, Goniewicz M, Phillips A, Myers-Smith K, West O, Hajek P. Effects of the use of electronic cigarettes with and without concurrent smoking on acrolein delivery POS4-33. In: Society for Research on Nicotine and Tobacco, 20th Annual Meeting, Seattle, Washington. 2014:13. [www.srnt.org/conferences/2014/pdf/SRNT_2014_Rapids_C.pdf]
    1. McRobbie H, Phillips A, Goniewicz ML, Smith KM, Knight-West O, Przulj D, et al. Effects of switching to electronic cigarettes with and without concurrent smoking on exposure to nicotine, carbon monoxide, and acrolein. Cancer Prevention Research (Philadelphia, Pa.) 2015;8(9):873-8. - PubMed
    1. NCT01714778. Toxins and Delivery in E-cigarette USers (TADEUS). clinicaltrials.gov/ct2/show/NCT01714778 (first received 26 October 2012).
Meier 2017 {published data only}
    1. Meier E, Wahlquist AE, Heckman BW, Cummings KM, Froeliger B, Carpenter MJ. A pilot randomized crossover trial of electronic cigarette sampling among smokers. Nicotine & Tobacco Research 2017;19(2):176-82. - PMC - PubMed
NCT02417467 {unpublished data only}
    1. NCT02417467. Evaluating the efficacy of e-cigarette use for smoking cessation (E3) trial. clinicaltrials.gov/show/NCT02417467 (accessed 17 February 2016).
NCT02648178 {published data only}
    1. NCT02648178. Evaluation of appeal and impact of e-cigarettes among chronic smokers with smoking-related cancers. clinicaltrials.gov/show/NCT02648178 (accessed 17 February 2016).
NCT02918630 {published data only}
    1. NCT02918630. E-cigarettes to promote smoking reduction among individuals with schizophrenia. clinicaltrials.gov/ct2/show/NCT02918630 (first received 5 July 2018).
Nides 2014 {published data only}
    1. NCT01898169. Evaluation of short-term safety and use patterns of an electronic nicotine delivery system. clinicaltrials.gov/ct2/show/NCT01898169 (first received 12 July 2013).
    1. Nides MA, Leischow SJ, Bhatter M, Simmons M. Nicotine blood levels and short-term smoking reduction with an electronic nicotine delivery system. American Journal of Health Behavior 2014;38(2):265-74. - PubMed
Oncken 2015 {published data only}
    1. NCT01775787. Effects of Electronic Cigarettes on Nicotine Concentrations (ECIG). clinicaltrials.gov/ct2/show/NCT01775787 (first received 25 January 2013).
    1. Oncken CA, Litt MD, McLaughlin LD, Burki NA. Nicotine concentrations with electronic cigarette use: effects of sex and flavor. Nicotine & Tobacco Research 2015;17(4):473-8. - PubMed
    1. Swedeh MA, Oncken C, Burki NK. Acute effects of electronic cigarettes on airway function in human subjects. In: American Thoracic Society International Conference Abstracts. Vol. 189. 2014:A4089.
Pacifici 2015 {published data only}
    1. Pacifici R, Pichini S, Graziano S, Pellegrini M, Massaro G, Beatrice F. Successful nicotine intake in medical assisted use of e-cigarettes: a pilot study. International Journal of Environmental Research and Public Health 2015;12(7):7638-46. - PMC - PubMed
Polosa 2011 {published data only}
    1. NCT01195597. Smoking cessation and reduction with an electronic nicotine delivery device (ENDD). clinicaltrials.gov/ct2/show/NCT01195597 (first received 6 September 2010).
    1. Polosa R, Caponnetto P, Morjaria JB, Papale G, Campagna D, Russo C. Effect of an electronic nicotine delivery device (e-cigarette) on smoking reduction and cessation: a prospective 6-month pilot study. BMC Public Health 2011;11:786. - PMC - PubMed
    1. Polosa R, Morjaria JB, Caponnetto P, Campagna D, Russo C, Alamo A, et al. Effectiveness and tolerability of electronic cigarette in real-life: a 24-month prospective observational study. Internal and Emergency Medicine 2014;9(5):537-46. - PubMed
Polosa 2014b {published data only}
    1. NCT02124200. High Cessation Rates in Smokers Using Personal Vaporizers (VAPECIG). clinicaltrials.gov/ct2/show/NCT02124200 (first received 28 April 2014).
    1. Polosa R, Caponnetto P, Maglia M, Morjaria JB, Russo C. Success rates with nicotine personal vaporizers: a prospective 6-month pilot study of smokers not intending to quit. BMC Public Health 2014;14:1159. - PMC - PubMed
Polosa 2015 {published data only}
    1. Polosa R, Caponnetto P, Cibella F, Le-Houezec J. Quit and smoking reduction rates in vape shop consumers: a prospective 12-month survey. International Journal of Environmental Research and Public Health 2015;12(4):3428-38. - PMC - PubMed
Pratt 2016 {published data only}
    1. Pratt SI, Sargent J, Daniels L, Santos MM, Brunette M. Appeal of electronic cigarettes in smokers with serious mental illness. Addictive Behaviors 2016;59:30-4. - PubMed
Pulvers 2018 {published data only}
    1. Pulvers K, Emami AS, Nollen NL, Romero DR, Strong DR, Benowitz NL, et al. Tobacco consumption and toxicant exposure of cigarette smokers using electronic cigarettes. Nicotine & Tobacco Research 2018;20(2):206-14. - PMC - PubMed
Smith 2020 {published and unpublished data}
    1. Smith TT, Heckman BW, Wahlquist AE, Cummings KM, Carpenter MJ. The impact of e-liquid propylene glycol and vegetable glycerin ratio on ratings of subjective effects, reinforcement value, and use in current smokers. Nicotine & Tobacco Research 2020;22(5):791-7. - PMC - PubMed
Stein 2016 {published data only}
    1. Stein MD, Caviness C, Grimone K, Audet D, Anderson BJ, Bailey GL. An open trial of electronic cigarettes for smoking cessation among methadone-maintained smokers. Nicotine & Tobacco Research 2016;18(5):1157-62. - PMC - PubMed
Strasser 2016 {published data only}
    1. Strasser AA, Souprountchouk V, Kaufmann A, Blazekovic S, Leone F, Benowitz NL, et al. Nicotine replacement, topography, and smoking phenotypes of e-cigarettes. Tobacco Regulatory Science 2016;2(4):352-62. - PMC - PubMed
Tseng 2016 {published data only}
    1. NCT02628964. Assessing the use of electronic cigarettes (e-cigarettes) as a harm reduction strategy. clinicaltrials.gov/show/NCT02628964 (accessed 17 February 2016).
    1. Tseng TY, Ostroff JS, Campo A, Gerard M, Kirchner T, Rotrosen J, et al. A randomized trial comparing the effect of nicotine versus placebo electronic cigarettes on smoking reduction among young adult smokers. Nicotine & Tobacco Research 2016;18(10):1937-43. - PMC - PubMed
Valentine 2018 {published data only}
    1. Valentine GW, Hefner K, Jatlow PI, Rosenheck RA, Gueorguieva R, Sofuoglu M. Impact of e-cigarettes on smoking and related outcomes in veteran smokers with psychiatric comorbidity. Journal of Dual Diagnosis 2018;14(1):2-13. - PMC - PubMed
Van Staden 2013 {published data only}
    1. Van Staden SR, Groenewald M, Engelbrecht R, Becker PJ, Hazelhurst LT. Carboxyhaemoglobin levels, health and lifestyle perceptions in smokers converting from tobacco cigarettes to electronic cigarettes. South African Medical Journal 2013;103(11):865-8. - PubMed
Veldheer 2019 {published and unpublished data}
    1. Lopez AA, Cobb CO, Yingst JM, Veldheer S, Hrabovsky S, Yen MS, et al. A transdisciplinary model to inform randomized clinical trial methods for electronic cigarette evaluation. BMC Public Health 2016;16(1):217. [PMCID:: PMC4778292] [PMID: ] - PMC - PubMed
    1. NCT02342795. Randomized controlled trial methods for novel tobacco products evaluation. clinicaltrials.gov/show/NCT02342795 (accessed 17 February 2016).
    1. Veldheer S, Yingst J, Midya V, Hummer B, Lester C, Krebs N, . Pulmonary and other health effects of electronic cigarette use among adult smokers participating in a randomized controlled smoking reduction trial. Addictive Behaviors 2019;91:95-101. - PMC - PubMed
Wadia 2016 {published data only}
    1. Wadia R, Booth V, Yap HF, Moyes DL. A pilot study of the gingival response when smokers switch from smoking to vaping. British Dental Journal 2016;221(11):722-6. - PubMed
Walele 2018 {published data only}
    1. Cravo AS, Bush J, Sharma G, Savioz R, Martin C, Craige S, et al. A randomised, parallel group study to evaluate the safety profile of an electronic vapour product over 12 weeks. Regulatory Toxicology and Pharmacology 2016;81:S1-S14. - PubMed
    1. NCT02029196. A randomised, parallel group, multi-centre study to evaluate the safety profile of the ITG EVP G1 product. clinicaltrials.gov/show/NCT02029196 (accessed 16 July 2014).
    1. NCT02143310. A multi-centre study to evaluate the safety of use of electronic vapour products for two years. clinicaltrials.gov/show/NCT02143310 (accessed 16 July 2014).
    1. Walele T, Bush J, Koch A, Savioz R, Martin C, O'Connell G. Evaluation of the safety profile of an electronic vapour product used for two years by smokers in a real-life setting. Regulatory Toxicology and Pharmacology 2018;92:226-38. - PubMed
Walker 2020 {published data only}
    1. NCT02521662. A randomised-controlled clinical trial to evaluate the effectiveness and safety of combining nicotine patches with e-cigarettes (with and without nicotine) plus behavioural support, on smoking abstinence. clinicaltrials.gov/show/NCT02521662 (accessed 17 February 2016).
    1. Walker N, Parag V, Verbiest M, Laking G, Laugesen M, Bullen C. Nicotine patches used in combination with e-cigarettes (with and without nicotine) for smoking cessation: a pragmatic, randomised trial. Lancet. Respiratory Medicine 2020;8(1):54-64. - PubMed
    1. Walker N, Verbiest M, Kurdziel T, Laking G, Laugesen M, Parag V, et al. Effectiveness and safety of nicotine patches combined with e-cigarettes (with and without nicotine) for smoking cessation: study protocol for a randomised controlled trial. BMJ Open 2019;9(2):e023659. - PMC - PubMed

References to studies excluded from this review

Adkison 2013 {published data only}
    1. Adkison SE, O'Connor RJ, Bansal-Travers M, Hyland A, Borland R, Yong HH, et al. Electronic nicotine delivery systems: international tobacco control four-country survey. American Journal of Preventive Medicine 2013;44(3):207-15. - PMC - PubMed
Al‐Delaimy 2015 {published data only}
    1. Al-Delaimy WK, Myers MG, Leas EC, Strong DR, Hofstetter CR. E-cigarette use in the past and quitting behavior in the future: a population-based study. American Journal of Public Health 2015;105(6):1213-9. - PMC - PubMed
    1. Donzelli A. E-cigarettes may impair ability to quit, but other explanations are possible. American Journal of Public Health 2015;105(11):e1. - PMC - PubMed
Anonymous 2019 {published data only}
    1. Anonymous. E-cigarettes best other cessation tools. Cancer Discovery 2019;9(4):OF3. - PubMed
Battista 2013 {published data only}
    1. Battista L, Di Iorio M, Tancredi M, Acconcia MC, Torromeo C, Barilla F, et al. Cardiovascular effects of electronic cigarettes. Circulation 2013;128:A16755.
Bianco 2019 {published data only}
    1. Bianco CL, Pratt SI, Ferron JC, Brunette MF. Electronic cigarette use during a randomized trial of interventions for smoking cessation among Medicaid beneficiaries with mental illness. Journal of Dual Diagnosis 2019;15(3):184-91. - PubMed
Biener 2015 {published data only}
    1. Biener L, Hargraves JL. A longitudinal study of electronic cigarette use among a population-based sample of adult smokers: association with smoking cessation and motivation to quit. Nicotine & Tobacco Research 2015;17(2):127-33. - PMC - PubMed
Biondi‐Zoccai 2019 {published data only}
    1. Biondi-Zoccai G, Sciarretta S, Bullen C, Nocella C, Violi F, Loffredo L, et al. Acute effects of heat-not-burn, electronic vaping, and traditional tobacco combustion cigarettes: the Sapienza University of Rome-Vascular Assessment of Proatherosclerotic Effects of Smoking ( SUR - VAPES ) 2 randomized trial. Journal of the American Heart Association 2019;8(6):e010455. - PMC - PubMed
Borderud 2014 {published data only}
    1. Barton MK. Electronic cigarettes did not help patients with cancer stop smoking. CA: a cancer journal for clinicians 2015;65(2):85-6. - PubMed
    1. Borderud SP, Li Y, Burkhalter JE, Sheffer CE, Ostroff JS. Electronic cigarette use among patients with cancer: characteristics of electronic cigarette users and their smoking cessation outcomes. Cancer 2014;120(22):3527-35. - PMC - PubMed
    1. Fillon M. Electronic cigarettes might not help cancer patients quit smoking. Journal of the National Cancer Institute 2015;107(1):496. - PubMed
Brose 2015 {published data only}
    1. Brose LS, Hitchman SC, Brown J, West R, McNeill A. Is the use of electronic cigarettes while smoking associated with smoking cessation attempts, cessation and reduced cigarette consumption? A survey with a 1-year follow-up. Addiction 2015;110(7):1160-8. - PMC - PubMed
    1. Brown J, West R, Beard E, Michie S, Shahab L, McNeill A. Prevalence and characteristics of e-cigarette users in Great Britain: Findings from a general population survey of smokers. Addictive Behaviors 2014;39(6):1120-5. - PMC - PubMed
    1. Hitchman SC, Brose LS, Brown J, Robson D, McNeill A. Associations between e-cigarette type, frequency of use, and quitting smoking: findings from a longitudinal online panel survey in Great Britain. Nicotine & Tobacco Research 2015;17(10):1187-94. - PMC - PubMed
Brown 2014a {published data only}
    1. Brown J, Beard E, Kotz D, Michie S, West R. Real-world effectiveness of e-cigarettes when used to aid smoking cessation: a cross-sectional population study. Addiction 2014;109(9):1531-40. - PMC - PubMed
Bullen 2010 {published data only}
    1. Bullen C, McRobbie H, Thornley S, Glover M, Lin R, Laugesen M. Effect of an electronic nicotine delivery device (e cigarette) on desire to smoke and withdrawal, user preferences and nicotine delivery: randomised cross-over trial. Tobacco Control 2010;19(2):98-103. - PubMed
Bullen 2018 {published data only}
    1. Bullen C, Verbiest M, Galea-Singer S, Kurdziel T, Laking G, Newcombe D, et al. The effectiveness and safety of combining varenicline with nicotine e-cigarettes for smoking cessation in people with mental illnesses and addictions: study protocol for a randomised-controlled trial. BMC Public Health 2018;18(1):596. - PMC - PubMed
Caponnetto 2019 {published data only}
    1. Caponnetto P, Maglia M, Polosa R. Efficacy of smoking cessation with varenicline plus counselling for e-cigarettes users (VAREVAPE): a protocol for a randomized controlled trial. Contemporary Clinical Trials Communications 2019;15:100412. - PMC - PubMed
Chaumont 2018 {published data only}
    1. Chaumont M, Becker B, Zaher W, Culie A, Deprez G, Melot C, et al. Differential Effects of E-Cigarette on Microvascular Endothelial Function, Arterial Stiffness and Oxidative Stress: a Randomized Crossover Trial. Scientific reports 2018;8(1):10378. - PMC - PubMed
Chaumont 2019 {published data only}
    1. Chaumont M, El Channan M, Bernard A, Lesage A, Deprez G, Van Muylem A, et al. Short-term high wattage e-cigarette cessation improves cardiorespiratory outcomes in regular users: a randomized crossover trial. Journal of Hypertension 2019;Conference: 29th European Meeting on Hypertension and Cardiovascular Protection, ESH 2019. Italy. 37(Supplement 1):e8-9.
Chausse 2015 {published data only}
    1. Chausse P, Naughton G, Dutheil F. Electronic cigarettes: the resistance value of the heating filament could be the key to lung toxicity. Chest 2015;148(1):e29-30. - PubMed
Choi 2014 {published data only}
    1. Choi K, Forster JL. Beliefs and experimentation with electronic cigarettes: a prospective analysis among young adults. American Journal of Preventive Medicine 2014;6(2):175-8. - PMC - PubMed
    1. Choi K Forster JL. Authors' Response to: Context on use is needed before public health recommendations are made about e-cigarettes. Americal Journal of Preventive Medicine 2014;46(6):e58-59. - PubMed
Chorti 2012 {published data only}
    1. Chorti M, Poulianiti K, Jamurtas A, Kostikas K, Tzatzarakis M, Vynias D, et al. Effects of active and passive electronic and tobacco cigarette smoking on lung function (P08-02). Toxicology Letters 2012;211:S64.
Collins 2019 {published data only}
    1. Collins SE, Nelson LA, Stanton J, Mayberry N, Ubay T, Taylor EM, et al. Harm reduction treatment for smoking (HaRT-S): findings from a single-arm pilot study with smokers experiencing chronic homelessness. Substance Abuse 2019;40(2):229-39. - PubMed
Cook 2019 {published data only}
    1. Cook R, Davidson P, Martin R. E-cigarettes helped more smokers quit than nicotine replacement therapy. BMJ 2019;365:l2036. - PubMed
Cox 2019a {published data only}
    1. Cox S, Dawkins L, Doshi J, Cameron J. Effects of e-cigarettes versus nicotine replacement therapy on short-term smoking abstinence when delivered at a community pharmacy. Addictive Behaviors Reports 2019;10:100202. - PMC - PubMed
Czogala 2012 {published data only}
    1. Czogala J, Cholewinski M, Kutek A, Zielinska-Danch W. Evaluation of changes in hemodynamic parameters after the use of electronic nicotine delivery systems among regular cigarette smokers. Przeglad Lekarski 2012;69(10):841-5. - PubMed
D'Ruiz 2017 {published data only}
    1. D'Ruiz CD, O'Connell G, Graff DW, Yan XS. Measurement of cardiovascular and pulmonary function endpoints and other physiological effects following partial or complete substitution of cigarettes with electronic cigarettes in adult smokers. Regulatory Toxicology and Pharmacology 2017;87:36-53. - PubMed
Dawkins 2012 {published data only}
    1. Dawkins L, Turner J, Hasna S, Soar K. The electronic-cigarette: effects on desire to smoke, withdrawal symptoms and cognition. Addictive Behaviors 2012;37(8):970-3. - PubMed
Dawkins 2013a {published data only}
    1. Dawkins L, Turner J, Crowe E. Nicotine derived from the electronic cigarette improves time-based prospective memory in abstinent smokers. Psychopharmacology 2013;227(3):377-84. - PubMed
Dawkins 2014 {published data only}
    1. Dawkins L, Corcoran O. Acute electronic cigarette use: nicotine delivery and subjective effects in regular users. Psychopharmacology 2014;231(2):401-7. - PubMed
Douptcheva 2013 {published data only}
    1. Douptcheva N, Gmel G, Studer J, Deline S, Etter JF. Use of electronic cigarettes among young Swiss men. Journal of Epidemiology & Community Health 2013;67(12):1075-6. - PubMed
Dutra 2014 {published data only}
    1. Dutra LM, Glantz SA. Electronic cigarettes and conventional cigarette use among U.S. adolescents: a cross-sectional study. JAMA Pediatrics 2014;168(7):610-7. - PMC - PubMed
Eissenberg 2010 {published data only}
    1. Eissenberg T. Electronic nicotine delivery devices: ineffective nicotine delivery and craving suppression after acute administration. Tobacco Control 2010;19(1):87-8. - PMC - PubMed
Elena Cavarretta 2019 {published data only}
    1. Elena Cavarretta E, Sciarretta S, Nocella C, Peruzzi M, Marullo AG, Loffredo L, et al. Subjective smoking satisfaction between heat-not-burn, electronic vaping, and traditional tobacco combustion cigarettes: a sub-analysis of the SUR-VAPES 2 trial. European Journal of Preventive Cardiology 2019;26 Supplement 1:S114.
Etter 2014 {published data only}
    1. Etter JF, Bullen C. A longitudinal study of electronic cigarette users. Addictive Behaviors 2014;39(2):491-4. - PubMed
Farsalinos 2012 {published data only}
    1. Farsalinos K, Tsiapras D, Kyrzopoulos S, Savvopoulou M, Avramidou E, Vasilopoulou D, et al. Acute effects of using an electronic nicotine-delivery device (e-cigarette) on myocardial function: comparison with the effects of regular cigarettes. European Heart Journal 2012;33:203. - PMC - PubMed
    1. Farsalinos KE, Romagna G, Tsiapras D, Kyrzopoulos S, Voudris V. Acute effects of using an electronic nicotine-delivery device (electronic cigarette) on myocardial function: comparison with the effects of regular cigarettes. BMC Cardiovascular Disorders 2014;14:78. - PMC - PubMed
Farsalinos 2013a {published data only}
    1. Farsalinos KE, Romagna G, Tsiapras D, Kyrzopoulos S, Voudris V. Evaluating nicotine levels selection and patterns of electronic cigarette use in a group of "vapers" who had achieved complete substitution of smoking. Substance Abuse: Research and Treatment 2013;7:139-46. - PMC - PubMed
Farsalinos 2013b {published data only}
    1. Farsalinos KE, Romagna G, Tsiapras D, Kyrzopoulos S, Spyrou A, Voudris V. Impact of flavour variability on electronic cigarette use experience: an internet survey. International Journal of Environmental Research & Public Health 2013;10(12):7272-82. - PMC - PubMed
Farsalinos 2013c {published data only}
    1. Farsalinos K, Tsiapras D, Kyrzopoulos S, Stefopoulos C, Spyrou A, Tsakalou M, et al. Immediate effects of electronic cigarette use on coronary circulation and blood carboxyhemoglobin levels: comparison with cigarette smoking. European Heart Journal 2013;34(Suppl 1):13.
Farsalinos 2013d {published data only}
    1. Farsalinos K, Tsiapras D, Kyrzopoulos S, Spyrou A, Stefopoulos C, Romagna G, et al. Effects of electronic cigarette use on the elastic properties of the ascending aorta in healthy subjects: comparison with the effects of tobacco cigarettes. European Heart Journal Cardiovascular Imaging 2013;14(Suppl 2):ii203.
Flouris 2012 {published data only}
    1. Flouris AD, Poulianiti KP, Chorti MS, Jamurtas AZ, Kouretas D, Owolabi EO, et al. Acute effects of electronic and tobacco cigarette smoking on complete blood count. Food and Chemical Toxicology 2012;50(10):3600-3. - PubMed
Flouris 2013 {published data only}
    1. Flouris AD, Chorti MS, Poulianiti KP, Jamurtas AZ, Kostikas K, Tzatzarakis MN, et al. Acute impact of active and passive electronic cigarette smoking on serum cotinine and lung function. Inhalation Toxicology 2013;25(2):91-101. - PubMed
Gmel 2016 {published data only}
    1. Gmel G, Baggio S, Mohler-Kuo M, Daeppen JB, Studer J. E-cigarette use in young Swiss men: is vaping an effective way of reducing or quitting smoking? Swiss Medical Weekly 2016;146:w14271. - PubMed
Gottlieb 2019 {published data only}
    1. Gottlieb MA. E-cigarettes versus nicotine-replacement therapy for smoking cessation. New England Journal of Medicine 2019;380(20):1974. - PubMed
Grana 2014b {published data only}
    1. Grana RA, Popova L, Ling PM. A longitudinal analysis of electronic cigarette use and smoking cessation. JAMA Internal Medicine 2014;174(5):812-3. - PMC - PubMed
James 2016 {published data only}
    1. James SA, Meier EM, Wagener TL, Smith KM, Neas BR, Beebe LA. E-Cigarettes for immediate smoking substitution in women diagnosed with cervical dysplasia and associated disorders. International Journal of Environmental Health Research 2016;13(3):E288. [DOI: 10.3390/ijerph13030288] - DOI - PMC - PubMed
    1. NCT01842828. E-Cigarettes as an addition to multi-component treatment for tobacco dependence: a pilot study. clinicaltrials.gov/show/NCT01842828 (accessed 16 July 2014).
Kasza 2013 {published data only}
    1. Kasza KA, Bansal-Travers M, O'Connor RJ, Compton WM, Kettermann A, Borek N, et al. Cigarette smokers' use of unconventional tobacco products and associations with quitting activity: findings from the ITC-4 U.S. cohort. Nicotine & Tobacco Research 2013;16(6):672-81. - PMC - PubMed
Kouretas 2012 {published data only}
    1. Kouretas D, Poulianiti K, Chorti M, Jamurtas A, Kostikas K, Tzatzarakis M, et al. Effects of electronic cigarette and tobacco cigarette smoking on complete blood count (P08-03). Toxicology Letters 2012;211:S64. - PubMed
Kousta 2019 {published data only}
    1. Kousta S. E-cigarettes for smoking cessation. Nature Human Behaviour 2019;3:322. - PubMed
Lechner 2015 {published data only}
    1. Lechner WV, Meier E, Wiener JL, Grant DM, Gilmore J, Judah MR, et al. The comparative efficacy of first- versus second-generation electronic cigarettes in reducing symptoms of nicotine withdrawal. Addiction 2015;110(5):862-7. - PubMed
Lee 2014 {published data only}
    1. Lee S, Grana RA, Glantz SA. Electronic cigarette use among Korean adolescents: a cross-sectional study of market penetration, dual use, and relationship to quit attempts and former smoking. Journal of Adolescent Health 2014;54(6):684-90. - PMC - PubMed
Manzoli 2015 {published data only}
    1. Manzoli L, Flacco ME, Fiore M, La Vecchia C, Marzuillo C, Gualano MR, et al. Electronic cigarettes efficacy and safety at 12 months: cohort study. PLOS One 2015;10(6):e0129443. - PMC - PubMed
    1. Manzoli L, La Vecchia C, Flacco ME, Capasso L, Simonetti V, Boccia S, et al. Multicentric cohort study on the long-term efficacy and safety of electronic cigarettes: study design and methodology. BMC Public Health 2013;13(1):883. - PMC - PubMed
    1. NCT01785537. The efficacy and safety of electronic cigarettes: a 5-year follow-up study. clinicaltrials.gov/ct2/show/NCT01785537 (first received 7 February 2013).
Marini 2014 {published data only}
    1. Marini S, Buonanno G, Stabile L, Ficco G. Short-term effects of electronic and tobacco cigarettes on exhaled nitric oxide. Toxicology and Applied Pharmacology 2014;278(1):9-15. - PubMed
Mayor 2019 {published data only}
    1. Mayor S. E-cigarettes help twice as many smokers quit as nicotine replacement therapy, trial finds. BMJ 2019;364:l473. - PubMed
Meltzer 2017 {published data only}
    1. Meltzer LR, Simmons VN, Sutton SK, Drobes DJ, Quinn GP, Meade CD, et al. A randomized controlled trial of a smoking cessation self-help intervention for dual users of tobacco cigarettes and e-cigarettes: intervention development and research design. Contemporary Clinical Trials 2017;60:56-62. - PMC - PubMed
Miura 2015 {published data only}
    1. Miura N, Yuki D, Minami N, Kakehi A, Futama Y. A study to investigate changes in the levels of biomarkers of exposure to selected cigarette smoke constituents in Japanese adult male smokers who switched to a non-combustion inhaler type of tobacco product. Regulatory Toxicology and Pharmacology 2015;71(3):498-506. - PubMed
NCT02487953a {unpublished data only}
    1. NCT02487953. Electronic nicotine delivery systems as a smoking cessation treatment. clinicaltrials.gov/ct2/show/NCT02487953 (first received 2 July 2015).
NCT02487953b {published data only}
    1. NCT02487953. Electronic Nicotine Delivery Systems (ENDS) as a smoking cessation treatment. clinicaltrials.gov/ct2/show/NCT02487953 (first received 2 July 2015).
NCT03036644 {published data only}
    1. NCT03036644. Comparison of electronic cigarettes and tobacco cigarettes on cardiovascular function and oxidative stress. clinicaltrials.gov/ct2/show/NCT03036644 (first received 30 January 2017).
NCT03575468 {published data only}
    1. NCT03575468. Enhanced e-cigarette coaching intervention for dual users of cigarettes and e-cigarettes. clinicaltrials.gov/ct2/show/NCT03575468 (first received 2 July 2018).
NCT04107779 {published data only}
    1. NCT04107779. Changes in biomarkers of cigarette smoke exposure after switching either exclusively or partly to JUUL ENDS. clinicaltrials.gov/ct2/show/NCT04107779 (first received 27 September 2019).
Nolan 2016 {published data only}
    1. Nolan M, Leischow S, Croghan I, Kadimpati S, Hanson A, Schroeder D, et al. Feasibility of electronic nicotine delivery systems in surgical patients. Nicotine & Tobacco Research 2016;18(8):1757-62. - PMC - PubMed
Palamidas 2014 {published data only}
    1. Palamidas A, Gennimata SA, Kaltsakas G, Tsikrika S, Vakali S, Gratziou C, et al. Acute effect of an e-cigarette with and without nicotine on lung function. Tobacco Induced Diseases 2014;12(Suppl 1):A34.
Pearson 2012 {published data only}
    1. Pearson JL, Richardson A, Niaura RS, Vallone DM, Abrams DB. E-cigarette awareness, use, and harm perceptions in US adults. American Journal of Public Health 2012;102(9):1758-66. - PMC - PubMed
Pokhrel 2013 {published data only}
    1. Pokhrel P, Fagan P, Little MA, Kawamoto CT, Herzog TA. Smokers who try e-cigarettes to quit smoking: findings from a multiethnic study in Hawaii. American Journal of Public Health 2013;103(9):e57-62. - PMC - PubMed
Polosa 2014a {published data only}
    1. Polosa R, Morjaria J, Caponnetto P, Caruso M, Strano S, Battaglia E, et al. Effect of smoking abstinence and reduction in asthmatic smokers switching to electronic cigarettes: evidence for harm reversal. International Journal of Environmental Research & Public Health 2014;11(5):4965-77. - PMC - PubMed
Popova 2013 {published data only}
    1. Ling PM, Popova L. Novel "Tobacco" product use and association with smoking cessation: a national study. Journal of General Internal Medicine 2012;27(2 Suppl):S254.
    1. Popova L, Ling PM. Alternative tobacco product use and smoking cessation: a national study. American Journal of Public Health 2013;103(5):923-30. - PMC - PubMed
Prochaska 2014 {published data only}
    1. Prochaska JJ, Grana RA. E-cigarette use among smokers with serious mental illness. PLOS One 2014;9(11):e113013. - PMC - PubMed
Russo 2018 {published data only}
    1. Russo C, Cibella F, Mondati E, Caponnetto P, Frazzetto E, Caruso M, et al. Lack of substantial post-cessation weight increase in electronic cigarettes users. International Journal of Environmental Research and Public Health 2018;15(4):581. - PMC - PubMed
Schober 2014 {published data only}
    1. Schober W, Szendrei K, Matzen W, Osiander-Fuchs H, Heitmann D, Schettgen T, et al. Use of electronic cigarettes (e-cigarettes) impairs indoor air quality and increases FeNO levels of e-cigarette consumers. International Journal of Hygiene and Environmental Health 2014;217(6):628-37. - PubMed
Siegel 2011 {published data only}
    1. Siegel MB, Tanwar KL, Wood KS. Electronic cigarettes as a smoking-cessation tool: results from an online survey. American Journal of Preventive Medicine 2011;40(4):472-5. - PubMed
Song 2020 {published data only}
    1. Song M-A, Reisinger SA, Freudenheim JL, Brasky TM, Mathe EA, McElroy JP, et al. Effects of electronic cigarette constituents on the human lung: a pilot clinical trial. Cancer Prevention Research 2020;13(2):145-52. - PMC - PubMed
St.Helen 2020 {published data only}
    1. StHelen G, Nardone N, Addo N, Dempsey D, Havel C, Jacob P, et al. Differences in nicotine intake and effects from electronic and combustible cigarettes among dual users. Addiction 2020;115(4):757-67. - PMC - PubMed
Stein 2019 {published data only}
    1. Stein JH, Korcarz CE. E-cigarettes versus nicotine-replacement therapy for smoking cessation. New England Journal of Medicine 2019;380(20):1973-4. - PubMed
Stower 2019 {published data only}
    1. Stower H. E-cigarettes to help smoking cessation. Nature Medicine 2019;25(3):358. - PubMed
Tsikrika 2014 {published data only}
    1. Tsikrika S, Vakali S, Gennimata SA, Palamidas A, Kaltsakas G, Koulouris N, et al. Short term use of an e-cig: influence on clinical symptoms, vital signs and eCO levels. Tobacco Induced Diseases 2014;12(Suppl 1):A30.
Tucker 2018 {published data only}
    1. Tucker MR, Laugesen M, Bullen C, Grace RC. Predicting short-term uptake of electronic cigarettes: effects of nicotine, subjective effects, and simulated demand. Nicotine & Tobacco Research 2018;20(10):1265-71. - PubMed
Tzatzarakis 2013 {published data only}
    1. Tzatzarakis MN, Tsitoglou KI, Chorti MS, Poulianiti KP, Jamurtas AZ, Koutedakis Y, et al. Acute and short term impact of active and passive tobacco and electronic cigarette smoking on inflammatory markers. Toxicology Letters 2013;221(Suppl):S86.
Vakali 2014 {published data only}
    1. Vakali S, Tsikrika S, Gennimata SA, Kaltsakas G, Palamidas A, Koulouris N, et al. E-cigarette acute effect on symptoms and airway inflammation: comparison of nicotine with a non-nicotine cigarette. Tobacco Induced Diseases 2014;12(Suppl 1):A35.
Valentine 2016 {published data only}
    1. Valentine GW, Jatlow PI, Coffman M, Nadim H, Gueorguieva R, Sofuoglu M. The effects of alcohol-containing e-cigarettes on young adult smokers. Drug and Alcohol Dependence 2016;159:272-6. - PMC - PubMed
Van Heel 2017 {published data only}
    1. Van Heel M, Van Gucht D, Vanbrabant K, Baeyens F. The importance of conditioned stimuli in cigarette and e-cigarette craving reduction by e-cigarettes. International Journal of Environmental Research and Public Health 2017;14(2):193. - PMC - PubMed
Vansickel 2010 {published data only}
    1. Vansickel AR, Cobb CO, Weaver MF, Eissenberg TE. A clinical laboratory model for evaluating the acute effects of electronic "cigarettes": nicotine delivery profile and cardiovascular and subjective effects. Cancer Epidemiology, Biomarkers & Prevention 2010;19(8):1945-53. - PMC - PubMed
Vansickel 2012 {published data only}
    1. Vansickel AR, Weaver MF, Eissenberg T. Clinical laboratory assessment of the abuse liability of an electronic cigarette. Addiction 2012;107(8):1493-500. - PMC - PubMed
Vansickel 2013 {published data only}
    1. Vansickel AR, Eissenberg T. Electronic cigarettes: effective nicotine delivery after acute administration. Nicotine & Tobacco Research 2013;15(1):267-70. - PMC - PubMed
Vardavas 2012 {published data only}
    1. Vardavas CI, Anagnostopoulos N, Kougias M, Evangelopoulou V, Connolly GN, Behrakis PK. Short-term pulmonary effects of using an electronic cigarette: Impact on respiratory flow resistance, impedance, and exhaled nitric oxide. Chest 2012;141(6):1400-6. - PubMed
Vickerman 2013 {published data only}
    1. Vickerman KA, Carpenter KM, Altman T, Nash CM, Zbikowski SM. Use of electronic cigarettes among state tobacco cessation quitline callers. Nicotine & Tobacco Research 2013;15(10):1787-91. - PubMed
Voos 2019 {published data only}
    1. Voos N, Kaiser L, Mahoney MC, Bradizza CM, Kozlowski LT, Benowitz NL, et al. Randomized within-subject trial to evaluate smokers' initial perceptions, subjective effects and nicotine delivery across six vaporized nicotine products. Addiction 2019;114(7):1236-48. - PMC - PubMed
Voos 2020 {published data only}
    1. Voos N, Smith D, Kaiser L, Mahoney MC, Bradizza CM, Kozlowski LT, et al. Effect of e-cigarette flavors on nicotine delivery and puffing topography: results from a randomized clinical trial of daily smokers. Psychopharmacology 2020;237(2):491-502. - PMC - PubMed
Wagener 2014 {published data only}
    1. Wagener TL, Meier E, Hale JJ, Oliver ER, Warner ML, Driskill LM, et al. Pilot investigation of changes in readiness and confidence to quit smoking after e-cigarette experimentation and 1 week of use. Nicotine & Tobacco Research 2014;16(1):108-14. - PubMed
Walele 2016a {published data only}
    1. Walele T, Sharma G, Savioz R, Martin C, Williams J. A randomised, crossover study on an electronic vapour product, a nicotine inhalator and a conventional cigarette. Part A: Pharmacokinetics. Regulatory Toxicity 2016;74:187-92. - PubMed
Walele 2016b {published data only}
    1. Walele T, Sharma G, Savioz R, Martin C, Williams J. A randomised, crossover study on an electronic vapour product, a nicotine inhalator and a conventional cigarette. Part B: Safety and subjective effects. Regulatory Toxicity 2016;74:193-9. - PubMed
Yan 2015 {published data only}
    1. Yan XS, D'Ruiz C. Effects of using electronic cigarettes on nicotine delivery and cardiovascular function in comparison with regular cigarettes. Regulatory Toxicology and Pharmacology 2015;71(1):24-34. - PubMed
Yuki 2017 {published data only}
    1. Yuki D, Sakaguchi C, Kikuchi A, Futamura Y. Pharmacokinetics of nicotine following the controlled use of a prototype novel tobacco vapor product. Regulatory Toxicology and Pharmacology 2017;87(2):30-5. - PubMed
Zhang 2019 {published data only}
    1. Zhang Y, Upson D. E-cigarettes versus nicotine-replacement therapy for smoking cessation. New England Journal of Medicine 2019;380(20):1973. - PubMed

References to ongoing studies

ACTRN12617001324303 {published data only}
    1. ACTRN12617001324303. Vaporised nicotine products versus oral forms of nicotine replacement therapy (NRT) products for tobacco smoking cessation among low-socioeconomic status (low-SES) smokers. anzctr.org.au/ACTRN12617001324303.aspx (first received 15 September 2017).
ACTRN12618000408280 {published data only}
    1. ACTRN12618000408280. Cessation and Relapse Prevention (CARP) Trial: Nicotine vaporisers compared to standard nicotine replacement therapy for smoking cessation among people with co-morbidities. www.anzctr.org.au/ACTRN12618000408280.aspx (first received 21 March 2018).
Begh 2019 {published data only}
    1. Begh R, Coleman T, Yardley L, Barnes R, Naughton F, Gilbert H, et al. Examining the effectiveness of general practitioner and nurse promotion of electronic cigarettes versus standard care for smoking reduction and abstinence in hardcore smokers with smoking-related chronic disease: protocol for a randomised controlled trial. Trials 2019;20(1):659. - PMC - PubMed
    1. ISRCTN59404712. GP/nurse promotion of e-cigarettes in supporting reduced smoking and cessation in smokers. www.isrctn.com/ISRCTN59404712 (first received 28 November 2017).
Berlin 2019 {published data only}
    1. Berlin I, Dautzenberg B, Lehmann B, Palmyre J, Liégey E, De Rycke Y, et al. Randomised, placebo-controlled, double-blind, double-dummy, multicentre trial comparing electronic cigarettes with nicotine to varenicline and to electronic cigarettes without nicotine: the ECSMOKE trial protocol. BMJ Open 2019;9(5):e028832. - PMC - PubMed
    1. NCT03630614. Randomized trial of electronic cigarettes with or without nicotine in smoking cessation (ECSMOKE). clinicaltrials.gov/ct2/show/NCT03630614 (first received 15 August 2018).
Caponnetto 2014 {published data only}
    1. Caponnetto P, Polosa R, Auditore R, Minutolo G, Signorelli M, Maglia M, et al. Smoking cessation and reduction in schizophrenia (SCARIS) with e-cigarette: study protocol for a randomized control trial. Trials [electronic resource] 2014;15:88. - PMC - PubMed
    1. NCT01979796. Antismoking effects of rlectronic cigarettes in subjects with schizophrenia and their potential influence on cognitive functioning: design of a randomized trial. Smoking Cessation And Reduction In Schizophrenia (The SCARIS Study). clinicaltrials.gov/show/NCT01979796 (accessed 16 July 2014).
Fraser 2015 {unpublished data only}
    1. ACTRN12612001210864. An open-label randomised pragmatic policy trial examining effectiveness of short-term use of Nicotine Replacement Therapy (NRT) vs short- or long-term use of NRT vs short- or long-term use of NRT or electronic nicotine delivery systems for smoking cessation in cigarette smokers. ACTRN12612001210864 (accessed 15 August 2016).
    1. Fraser D, Borland R, Gartner C. Protocol for a randomised pragmatic policy trial of nicotine products for quitting or long-term substitution in smokers. BMC Public Health 2015;15:1026. - PMC - PubMed
ISRCTN13288677 {published data only}
    1. ISRCTN13288677. Can electronic cigarettes and nicotine replacement treatment help reduce smoking in smokers who struggle to quit? www.isrctn.com/ISRCTN13288677 (first received 17 March 2017).
Klonizakis 2017 {published data only}
    1. Klonizakis M, Crank H, Gumber A, Brose LS. Smokers making a quit attempt using e-cigarettes with or without nicotine or prescription nicotine replacement therapy: Impact on cardiovascular function (ISME-NRT) - a study protocol. BMC Public Health 2017;17(1):293. - PMC - PubMed
    1. NCT03061253. E-cigarettes and cardiovascular function (ISME-NRT). clinicaltrials.gov/ct2/show/NCT03061253 (first received 23 February 2017).
NCT01842828 {published data only}
    1. NCT01842828. E-Cigarettes as an addition to multi-component treatment for tobacco dependence: a pilot study. clinicaltrials.gov/show/NCT01842828 (accessed 16 July 2014).
NCT01989923 {published data only}
    1. NCT01989923. Immediate smoking cessation for patients at risk for cervical dysplasia, cervical cancer and lower genital tract dysplasia and cancer - a feasibility study comparing nicotine replacement therapy with the electronic nicotine delivery system. clinicaltrials.gov/show/NCT01989923 (accessed 16 July 2014).
NCT02004171 {published data only}
    1. NCT02004171. Electronic nicotine delivery devices (ENDDs) or nicotine inhaler for smoking cessation. clinicaltrials.gov/show/NCT02004171 (accessed 16 July 2014).
NCT02124187 {published data only}
    1. NCT02124187. Smoking cessation and reduction in depression (SCARID). clinicaltrials.gov/show/NCT02124187 (accessed 16 July 2014).
NCT02261363 {published data only}
    1. NCT02261363. A mixed method EMA assessment of cognition and behavior among new ENDS users: an observational cohort study. clinicaltrials.gov/show/NCT02261363 2014 (accessed 15 August 2016).
    1. Pearson JL, Smiley SL, Rubin LF, Anesetti-Rothermel A, Elmasry H, Davis M, et al. The Moment Study: protocol for a mixed method observational cohort study of the Alternative Nicotine Delivery Systems (ANDS) initiation process among adult cigarette smokers. BMJ Open 2016;6(4):e011717. - PMC - PubMed
NCT02398487 {published data only}
    1. NCT02398487. Head-to-head comparison of personal vaporizers versus cigalike: prospective 6-month randomized control design study. clinicaltrials.gov/show/NCT02398487 (accessed 17 February 2016).
NCT02487953 {published data only}
    1. NCT02487953. Electronic nicotine delivery systems (ENDS) as a smoking cessation treatment. clinicaltrials.gov/show/NCT02487953 (accessed 17 February 2016).
NCT02527980 {published data only}
    1. NCT02527980. E-cigarettes: dynamic patterns of use and health effects. clinicaltrials.gov/show/NCT02527980 (accessed 17 February 2016).
NCT02590393 {published data only}
    1. NCT02590393. The role of nicotine and non-nicotine alkaloids in e-cigarette use and dependence. clinicaltrials.gov/show/NCT02590393 (accessed 17 February 2016).
NCT02635620 {published data only}
    1. NCT02635620. Changes in lung function parameters, bronchial reactivity, state of health and smoking behaviour associated with changing from conventional smoking to electronic cigarettes. clinicaltrials.gov/show/NCT02635620 (accessed 17 February 2016).
NCT03589989 {published data only}
    1. NCT03589989. The ESTxENDS Trial- Electronic Nicotine Delivery Systems (ENDS/Vaporizer/E-cigarette) as an aid for smoking cessation. (ESTxENDS). clinicaltrials.gov/ct2/show/record/NCT03589989 (first received 18 July 2018).
    1. NCT03603340. The ESTxENDS Trial- Effects of Using Electronic Nicotine Delivery Systems (ENDS/Vaporizer/E-cig) on depression (ESTxENDS). clinicaltrials.gov/show/NCT03603340 (first received 27 July 2018).
    1. NCT03603353. The ESTxENDS Trial- Effects of Using Electronic Nicotine Delivery Systems (ENDS/Vaporizer/E-cig) on sleep quality. (ESTxENDS). clinicaltrials.gov/show/NCT03603353 (first received 27 July 2018).
    1. NCT03612336. The ESTxENDS Trial- Metabolic Effects of Using Electronic Nicotine Delivery Systems (ENDS/Vaporizer/E-cig) (ESTxENDS). clinicaltrials.gov/show/NCT03612336 (first received 2 August 2018).
    1. NCT03612375. ESTxENDS Trial-Oxidative Stress Induced by Electronic Nicotine Delivery Systems (ENDS/Vaporizer/E-cig) measured in urine (ESTxENDS). clinicaltrials.gov/show/NCT03612375 (first received 2 August 2018).
NCT03700112 {published data only}
    1. NCT03700112. Clinical study comparing 7 ENDS products and 1 combustible cigarette using 2 delivery methods. clinicaltrials.gov/ct2/show/NCT03700112 (first received 7 December 2018).
NCT03962660 {published data only}
    1. NCT03962660. Harm Reduction for Tobacco Smoking with support of Tobacco-Rreplacing Electronic Nicotine Delivery Systems (HaRTS-TRENDS). clinicaltrials.gov/ct2/show/record/NCT03962660 (first received 24 May 2019).
NCT04063267 {published data only}
    1. NCT04063267. Electronic cigarettes as a harm reduction strategy in individuals with substance use disorder. clinicaltrials.gov/ct2/show/NCT04063267 (first received 21 August 2019).
NTR6224 {published data only}
    1. NTR6224. Electronic cigarettes: an intervention for dual-users. www.who.int/trialsearch/Trial2.aspx?TrialID=NTR6224 (first received 12 January 2017).

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