Electronic cigarettes for smoking cessation

Jamie Hartmann-Boyce, Hayden McRobbie, Nicola Lindson, Chris Bullen, Rachna Begh, Annika Theodoulou, Caitlin Notley, Nancy A Rigotti, Tari Turner, Ailsa R Butler, Peter Hajek, Jamie Hartmann-Boyce, Hayden McRobbie, Nicola Lindson, Chris Bullen, Rachna Begh, Annika Theodoulou, Caitlin Notley, Nancy A Rigotti, Tari Turner, Ailsa R Butler, Peter Hajek

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.

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

2
Study flow diagram for review update 2016

3
Study flow diagram for original review, 2014

4
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

**1.1. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 1: Smoking cessation

**1.2. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 2: Adverse events

**1.3. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 3: Serious adverse events

**1.4. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 4: Carbon monoxide (ppm)

**1.5. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 5: Heart rate (bpm)

**1.6. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 6: Systolic blood pressure

**1.7. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 7: Blood oxygen saturation

**1.8. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 8: 3‐HPMA (pmol/mg creatinine)

**1.9. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 9: NNAL (pmol/mg creatinine))

**1.10. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 10: 2‐HPMA (pmol/mg creatinine)

**1.11. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 11: HMPMA (pmol/mg creatinine)

**1.12. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 12: PheT (pmol/mg creatinine)

**1.13. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 13: CEMA (pmol/mg creatinine)

**1.14. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 14: AAMA (pmol/mg creatinine)

**1.15. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 15: FEV1 (ml)

**1.16. Analysis**
Comparison 1: Nicotine EC versus NRT, Outcome 16: FEV1/FVC (%)

**2.1. Analysis**
Comparison 2: Nicotine EC versus varenicline, Outcome 1: Smoking cessation

**2.2. Analysis**
Comparison 2: Nicotine EC versus varenicline, Outcome 2: Serious adverse events

**3.1. Analysis**
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 1: Smoking cessation

**3.2. Analysis**
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 2: Adverse events

**3.3. Analysis**
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 3: Serious adverse events

**3.4. Analysis**
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 4: Carbon monoxide (ppm)

**3.5. Analysis**
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 5: Heart rate

**3.6. Analysis**
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 6: Systolic blood pressure

**3.7. Analysis**
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 7: FeNO (ppb)

**3.8. Analysis**
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 8: FEV1 (l)

**3.9. Analysis**
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 9: FVC (l)

**3.10. Analysis**
Comparison 3: Nicotine EC versus non‐nicotine EC, Outcome 10: FEV1/FVC

**4.1. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 1: Smoking cessation

**4.2. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 2: Adverse events

**4.3. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 3: Serious adverse events

**4.4. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 4: Carbon monoxide (ppm)

**4.5. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 5: Heart rate (bpm)

**4.6. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 6: Systolic blood pressure

**4.7. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 7: Blood oxygen saturation

**4.8. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 8: 3‐HPMA (SMD)

**4.9. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 9: NNAL (SMD)

**4.10. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 10: 2‐HPMA (pmol/mg creatinine)

**4.11. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 11: HMPMA (pmol/mg creatinine)

**4.12. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 12: PheT (pmol/mg creatinine)

**4.13. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 13: CEMA (pmol/mg creatinine)

**4.14. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 14: AAMA (pmol/mg creatinine)

**4.15. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 15: S‐PMA (nanograms)

**4.16. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 16: FVC (litres)

**4.17. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 17: FEV1 (litres)

**4.18. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 18: FEF 25‐75 (litres/second))

**4.19. Analysis**
Comparison 4: Nicotine EC versus behavioural support only/no support, Outcome 19: PEF 25‐75 (litres/minute)

**5.1. Analysis**
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 1: Smoking cessation

**5.2. Analysis**
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 2: Adverse events

**5.3. Analysis**
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 3: Serious adverse events

**5.4. Analysis**
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 4: Carbon monoxide (ppm)

**5.5. Analysis**
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 5: FeNO (ppb)

**5.6. Analysis**
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 6: FEV1 (%)

**5.7. Analysis**
Comparison 5: Nicotine EC + NRT versus non‐nicotine EC + NRT, Outcome 7: FVC (%)

**6.1. Analysis**
Comparison 6: Nicotine EC + NRT versus NRT, Outcome 1: Smoking cessation

**6.2. Analysis**
Comparison 6: Nicotine EC + NRT versus NRT, Outcome 2: Adverse events

**6.3. Analysis**
Comparison 6: Nicotine EC + NRT versus NRT, Outcome 3: Serious adverse events

**7.1. Analysis**
Comparison 7: Higher versus lower nicotine content, Outcome 1: Serious adverse events

**7.2. Analysis**
Comparison 7: Higher versus lower nicotine content, Outcome 2: Carbon monoxide (ppm)

**7.3. Analysis**
Comparison 7: Higher versus lower nicotine content, Outcome 3: Heart rate

**7.4. Analysis**
Comparison 7: Higher versus lower nicotine content, Outcome 4: Systolic blood pressure

**7.5. Analysis**
Comparison 7: Higher versus lower nicotine content, Outcome 5: FeNO (ppb)

**7.6. Analysis**
Comparison 7: Higher versus lower nicotine content, Outcome 6: FEV1 (l)

**7.7. Analysis**
Comparison 7: Higher versus lower nicotine content, Outcome 7: FVC (l)

**7.8. Analysis**
Comparison 7: Higher versus lower nicotine content, Outcome 8: FEV1/FVC

**8.1. Analysis**
Comparison 8: Non‐nicotine EC versus behavioural support only/no support, Outcome 1: Smoking cessation

**9.1. Analysis**
Comparison 9: Non‐nicotine EC + NRT versus NRT, Outcome 1: Smoking cessation

**9.2. Analysis**
Comparison 9: Non‐nicotine EC + NRT versus NRT, Outcome 2: Adverse events

**9.3. Analysis**
Comparison 9: Non‐nicotine EC + NRT versus NRT, Outcome 3: Serious adverse events

**10.1. Analysis**
Comparison 10: Non‐nicotine EC versus NRT, Outcome 1: Smoking cessation

**10.2. Analysis**
Comparison 10: Non‐nicotine EC versus NRT, Outcome 2: Adverse events

**10.3. Analysis**
Comparison 10: Non‐nicotine EC versus NRT, Outcome 3: Serious adverse events

References

References to studies included in this review Adriaens 2014 {published data only}

1. Adriaens K, Van Gucht D, Declerck P, Baeyens F. Effectiveness of the electronic cigarette: an eight-week Flemish study with six-month follow-up on smoking reduction, craving and experienced benefits and complaints. International Journal of Environmental Research and Public Health 2014;11(11):11220-48.

Baldassarri 2018 {published data only}

1. Baldassarri SR, Bernstein SL, Chupp GL, Slade MD, Fucito LM, Toll BA. Electronic cigarettes for adults with tobacco dependence enrolled in a tobacco treatment program: a pilot study. Addictive Behaviors May 2018;80:1-5.
1. NCT02498145. Short term effects of electronic cigarettes in tobacco dependent adults. (accessed 17 February 2016).

Bell 2017 {unpublished data only}

1. ACTRN12616001641482. Tobacco harm reduction with vaporised nicotine (THRiVe): feasibility study. (first received 28 November 2016).
1. Bell S, Dean J, Gilks C, Boyd MA, Fitzgerald L, Mutch A, et al. Tobacco harm reduction with vaporised nicotine (THRiVe): the study protocol of an uncontrolled feasibility study of novel nicotine replacement products among people living with HIV who smoke. International Journal of Environmental Research and Public Health 2017;14(7):799.

Bullen 2013 {published data only}

1. Bullen C, Howe C, Laugesen M, McRobbie H, Parag V, Williman J, et al. Electronic cigarettes and smoking cessation: a quandary? - Authors' reply. Lancet 2014;383(9915):408-9.
1. Bullen C, Howe C, Laugesen M, McRobbie H, Parag V, Williman J, et al. Electronic cigarettes for smoking cessation: a randomised controlled trial. Lancet 2013;382(9905):1629-37.
1. Bullen C, Howe C, Laugesen M, McRobbie H, Parag V, Williman J. Do electronic cigarettes help smokers quit? Results from a randomised controlled trial [Abstract]. In: European Respiratory Society Annual Congress, 2013 September 7 - 11, Barcelona, Spain. Vol. 42. 2013:215s-[P1047].
1. Bullen C, Williman J, Howe C, Laugesen M, McRobbie H, Parag V, et al. Study protocol for a randomised controlled trial of electronic cigarettes versus nicotine patch for smoking cessation. BMC Public Health 2013;13:210.
1. O'Brien B, Knight-West O, Walker N, Parag V, Bullen C. E-cigarettes versus NRT for smoking reduction or cessation in people with mental illness: secondary analysis of data from the ASCEND trial. Tobacco Induced Diseases 2014;13(1):5.

Caponnetto 2013a {published data only}

1. Campagna D, Cibella F, Caponnetto P, Amaradio MD, Caruso M, Morjaria JB, et al. Changes in breathomics from a 1-year randomized smoking cessation trial of electronic cigarettes. European Journal of Clinical Investigation 2016;46(8):698-706.
1. Caponnetto P, Campagna D, Cibella F, Morjaria JB, Caruso M, Russo C, et al. EffiCiency and Safety of an eLectronic cigAreTte (ECLAT) as tobacco cigarettes substitute: a prospective 12-month randomized control design study. PlOS One 2013;8(6):e66317.
1. Cibella F, Campagna D, Caponnetto P, Amaradio MD, Caruso M, Russo C, et al. Lung function and respiratory symptoms in a randomized smoking cessation trial of electronic cigarettes. Clinical Science 2016;130(21):1929–37.
1. Farsalinos K, Cibella F, Caponnetto P, Campagna D, Morjaria JB, Battaglia E, et al. Effect of continuous smoking reduction and abstinence on blood pressure and heart rate in smokers switching to electronic cigarettes. Internal and Emergency Medicine 2016;11(1):85-94.
1. NCT01164072. Efficacy and safety of an electronic nicotine delivery device (e-cigarette). (first received 16 July 2010).
1. NCT01194583. Efficacy and safety of an electronic nicotine delivery device (e-cigarette) without nicotine cartridges. (first received 3 September 2010).
1. Russo C, Cibella F, Caponnetto P, Campagna D, Maglia M, Frazzetto E, et al. Evaluation of post cessation weight gain in a 1-year randomized smoking cessation trial of electronic cigarettes. Scientific Reports 2016;6:18763.

Caponnetto 2013b {published data only}

1. Caponnetto P, Auditore R, Russo C, Cappello GC, Polosa R. Impact of an electronic cigarette on smoking reduction and cessation in schizophrenic smokers: a prospective 12-month pilot study. International Journal of Environmental Research and Public Health 2013;10(2):446-61.
1. Minutolo G, Caponnetto P, Auditore R, Russo C, Polosa R. Management of smoking reduction and cessation in inpatients with schizophrenia: Impact of electronic cigarettes. European Neuropsychopharmacology 2013;23:S581-2.

Carpenter 2017 {published data only}

1. Carpenter MJ, Heckman BW, Wahlquist AE, Wagener TL, Goniewicz ML, Gray KM, et al. A naturalistic, randomized pilot trial of e-cigarettes: uptake, exposure, and behavioral effects. Cancer Epidemiology, Biomarkers & Prevention 2017;26(12):1795-803.
1. NCT02357173. A trial of e-cigarettes: natural uptake, patterns and impact of use. (accessed 17 February 2016).
1. Smith TT, Wahlquist AE, Heckman BW, Cummings KM, Carpenter MJ. Impact of e-cigarette sampling on cigarette dependence and reinforcement value. Nicotine & Tobacco Research 2020;22(2):297-301.

Ely 2013 {published data only}

1. Ely J. Evaluation of the use of electric cigarettes in a rural smoking cessation program. Available online at: [no longer available] 2013 (accessed 1st November 2014).

Felicione 2019 {published data only}

1. Felicione NJ, Enlow P, Elswick D, Long D, Sullivan CR, Blank MD. A pilot investigation of the effect of electronic cigarettes on smoking behavior among opioid-dependent smokers. Addictive Behaviors 2019;91:45-50.

George 2019 {published data only}

1. George J, Hussain M, Vadiveloo T, Ireland S, Hopkinson P, Struthers AD, et al. Cardiovascular effects of switching from tobacco cigarettes to electronic cigarettes. Journal of the American College of Cardiology 2019;74(25):3112-20.
1. NCT02878421. Vascular EffectS of regUlar cigarettes Versus electronIc cigarette USe (VESUVIUS). (first received 25 August 2016).

Goniewicz 2017 {published data only}

1. ACTRN12617000849392. The QuitNic Study: a pilot study of electronic nicotine devices for smoking cessation with drug and alcohol clients. (first received 8 June 2017).
1. Goniewicz ML, Gawron M, Smith DM, Peng M, Jacob P 3rd, Benowitz NL. Exposure to nicotine and selected toxicants in cigarette smokers who switched to electronic cigarettes: a longitudinal within-subjects observational study. Nicotine & Tobacco Research 2017;19(2):160-7.

Guillaumier 2018 {unpublished data only}

1. Guillaumier A, Manning V, Wynne O, Gartner C, Borland R, Baker AL, et al. Electronic nicotine devices to aid smoking cessation by alcohol- and drug-dependent clients: protocol for a pilot randomised controlled trial. Trials 2018;19:415.

Hajek 2015a {published data only}

1. Hajek P, Corbin L, Ladmore D, Spearing E. Adding e-cigarettes to specialist stop-smoking treatment: City of London pilot project. Journal of Addiction Research & Therapy 2015;6(244):(online ahead of print). [DOI: 10.4172/2155-6105.1000244]

Hajek 2019 {published and unpublished data}

1. Hajek P, Phillips-Waller A, Przulj D, Pesola F, Myers Smith K, Bisal N, et al. A randomized trial of e-cigarettes versus nicotine-replacement therapy. New England Journal of Medicine 2019;380(7):629-37.
1. ISRCTN60477608. The efficacy of e-cigarettes compared with nicotine replacement therapy, when used within the UK stop smoking service. 2014 (first received 2 April 2015).
1. Li J, Hajek P, Pesola F, Wu Q, Phillips-Waller A, Przulj D, et al. Cost-effectiveness of e-cigarettes compared with nicotine replacement therapy in stop smoking services in England (TEC study): a randomized controlled trial. Addiction 2020;115(3):507-17.

Halpern 2018 {published data only}

1. Halpern SD, Harhay MO, Saulsgiver K, Brophy C, Troxel AB, Volpp KG. A pragmatic trial of e-cigarettes, incentives, and drugs for smoking cessation. New England Journal of Medicine 2018;378(24):2302-10.
1. NCT02328794. Randomized clinical trial to reduce harm from tobacco. (accessed 17 February 2016).

Hatsukami 2020 {published and unpublished data}

1. Hatsukami D, Meier E, Lindgren BR, Anderson A, Reisinger S, Norton K, et al. A randomized clinical trial examining the effects of instructions for electronic cigarette use on smoking-related behaviors, and biomarkers of exposure. Nicotine & Tobacco Research 2020;22(9):1524-32. [DOI: 10.1093/ntr/ntz233]

Hickling 2019 {published data only}

1. Hickling LM, Perez-Iglesias R, McNeill A, Dawkins L, Moxham J, Ruffell T, et al. A pre-post pilot study of electronic cigarettes to reduce smoking in people with severe mental illness. Psychological Medicine 2019;49(6):1033-40.
1. NCT02212041. Acceptability, patterns of use and safety of electronic cigarette in people with mental illness: a pilot study. (accessed 17 February 2016).

Holliday 2019 {published data only}

1. Holliday R, Preshaw PM, Ryan V, Sniehotta FF, McDonald S, Bauld L, et al. A feasibility study with embedded pilot randomised controlled trial and process evaluation of electronic cigarettes for smoking cessation in patients with periodontitis. Pilot and Feasibility Studies 2019;5:74.
1. ISRCTN17731903. Feasibility study of e-cigarettes in periodontitis. (first received 27 September 2016).

Humair 2014 {published data only}

1. Humair J-P, Tango R. Can e-cigarette help patients to reduce or stop smoking in primary care practice? Journal of General Internal Medicine 2014;29:S480.

Ikonomidis 2018 {published data only}

1. Ikonomidis I, Vlastos D, Kourea K, Kostelli G, Varoudi M, Pavlidis G, et al. Electronic cigarette smoking increases arterial stiffness and oxidative stress to a lesser extent than a single conventional cigarette: an acute and chronic study. Circulation 2018;137(3):303-6.
1. NCT03039920. The effects of electronic cigarette smoking on the arterial wall and endothelial glycocalyx properties of smokers. (first received 1 February 2017).

Ioakeimidis 2018 {published data only}

1. Ioakeimidis N, Vlachopoulos C, Georgakopoulos C, Abdelrasoul M, Skliros N, Katsi V, et al. Smoking cessation rates with varenicline and electronic cigarettes in relapsed smokers with a history of acute coronary syndrome. European Heart Journal 2018;39(Suppl_1):242.

ISRCTN14140672 {unpublished data only}

1. ISRCTN14140672. Exploring the use and uptake of e-cigarettes for homeless smokers. (first received 7 November 2018).

Kumral 2016 {published data only}

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.

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.
1. NCT02482233. A pilot randomized controlled clinical trial - "Electronic nicotine delivery device (e-cigarette) for perioperative smoking cessation in veterans". (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).
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.

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: ]
1. NCT02422914. Benefits of tobacco free cigarette among heavy smokers undergoing a lung cancer screening program: a randomized controlled study. (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.

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. []
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.
1. NCT01714778. Toxins and Delivery in E-cigarette USers (TADEUS). (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.

NCT02417467 {unpublished data only}

1. NCT02417467. Evaluating the efficacy of e-cigarette use for smoking cessation (E3) trial. (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. (accessed 17 February 2016).

NCT02918630 {published data only}

1. NCT02918630. E-cigarettes to promote smoking reduction among individuals with schizophrenia. (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. (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.

Oncken 2015 {published data only}

1. NCT01775787. Effects of Electronic Cigarettes on Nicotine Concentrations (ECIG). (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.
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.

Polosa 2011 {published data only}

1. NCT01195597. Smoking cessation and reduction with an electronic nicotine delivery device (ENDD). (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.
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.

Polosa 2014b {published data only}

1. NCT02124200. High Cessation Rates in Smokers Using Personal Vaporizers (VAPECIG). (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.

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.

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.

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.

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.

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.

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.

Tseng 2016 {published data only}

1. NCT02628964. Assessing the use of electronic cigarettes (e-cigarettes) as a harm reduction strategy. (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.

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.

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.

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: ]
1. NCT02342795. Randomized controlled trial methods for novel tobacco products evaluation. (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.

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.

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.
1. NCT02029196. A randomised, parallel group, multi-centre study to evaluate the safety profile of the ITG EVP G1 product. (accessed 16 July 2014).
1. NCT02143310. A multi-centre study to evaluate the safety of use of electronic vapour products for two years. (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.

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. (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.
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.

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.

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.
1. Donzelli A. E-cigarettes may impair ability to quit, but other explanations are possible. American Journal of Public Health 2015;105(11):e1.

Anonymous 2019 {published data only}

1. Anonymous. E-cigarettes best other cessation tools. Cancer Discovery 2019;9(4):OF3.

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.

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.

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.

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.
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.
1. Fillon M. Electronic cigarettes might not help cancer patients quit smoking. Journal of the National Cancer Institute 2015;107(1):496.

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.
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.
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.

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.

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.

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.

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.

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.

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.

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.
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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.
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.

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.

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.

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.

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.

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.

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.

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.

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]
1. NCT01842828. E-Cigarettes as an addition to multi-component treatment for tobacco dependence: a pilot study. (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.

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.

Kousta 2019 {published data only}

1. Kousta S. E-cigarettes for smoking cessation. Nature Human Behaviour 2019;3:322.

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.

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.

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.
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.
1. NCT01785537. The efficacy and safety of electronic cigarettes: a 5-year follow-up study. (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.

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.

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.

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.

NCT02487953a {unpublished data only}

1. NCT02487953. Electronic nicotine delivery systems as a smoking cessation treatment. (first received 2 July 2015).

NCT02487953b {published data only}

1. NCT02487953. Electronic Nicotine Delivery Systems (ENDS) as a smoking cessation treatment. (first received 2 July 2015).

NCT03036644 {published data only}

1. NCT03036644. Comparison of electronic cigarettes and tobacco cigarettes on cardiovascular function and oxidative stress. (first received 30 January 2017).

NCT03575468 {published data only}

1. NCT03575468. Enhanced e-cigarette coaching intervention for dual users of cigarettes and e-cigarettes. (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. (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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Stower 2019 {published data only}

1. Stower H. E-cigarettes to help smoking cessation. Nature Medicine 2019;25(3):358.

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.

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.

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.

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References to other published versions of this review Hartmann‐Boyce 2016

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Source: PubMed

Electronic cigarettes for smoking cessation

Abstract

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