Vaping
In randomized trials, nicotine e-cigarettes led to more people stopping smoking than nicotine replacement, about 4 more quitters per 100, with similar serious adverse events. Most of those quitters kept vaping. As an exposure, vaping is linked to asthma, COPD and later smoking in young people, and briefly raises heart rate. Long-term harms are largely unknown.
Checked 2026-11-13
- Status
- A daily life factor, not a product. E-cigarettes themselves are regulated in the US by the FDA as tobacco products.
- Also called
- e-cigarettes, e-cigs, electronic cigarettes, vapes, vape pens, pod vapes, disposable vapes, ENDS, electronic nicotine delivery systems, Juul, vaping to quit smoking, switching to vaping, EVALI
- Studied for
- quitting smoking, cutting down cigarettes, less harm than smoking, breathing after switching, stress relief, focus, being harmless water vapor
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help6
- StrongShown to help more people stop smoking for at least 6 months than nicotine replacement therapy, about 4 more quitters per 100, in high-certainty pooled trials.
- StrongShown to help more people stop smoking than e-cigarettes without nicotine, about 2 more quitters per 100, in two meta-analyses of randomized trials.
- ModerateShown to help more people stop smoking than behavioral support alone or no support, in pooled trials rated low in certainty because of risk of bias.
- ModerateShown to lower exhaled carbon monoxide and most measured markers of potential harm in people who switched fully from cigarettes to e-cigarettes in quit trials.
- LimitedOne trial found better blood vessel function within 1 month in smokers who switched to e-cigarettes, with or without nicotine, than in those who kept smoking.
- LimitedOne trial found cough and phlegm fell more over a year with e-cigarettes than with nicotine replacement, with no difference in wheezing or shortness of breath.
Reported risks8
- StrongLinked to three to four times the odds of later starting to smoke in young people who had vaped, in two meta-analyses of longitudinal studies.Very common
- ModerateOne trial found throat or mouth irritation in 65% of e-cigarette users against 51% with nicotine replacement. Pooled trials found overall adverse events similar to nicotine replacement.Very common
- LimitedOne trial found 80% of people who quit with e-cigarettes were still vaping a year later, against 9% still using nicotine replacement.Very common
- ModerateShown to raise heart rate and blood pressure slightly right after vaping, in one meta-analysis of 14 short studies.How often is not known
- ModerateLinked to more asthma and COPD in people who vape, after accounting for cigarette smoking, in one meta-analysis of population studies.How often is not known
- LimitedCase series: a US outbreak of lung injury in 2019 and 2020 hospitalized 2,668 people, mostly users of THC vaping products, with vitamin E acetate found in most cases tested.How often is not known
- LimitedLimited evidence: a review of five observational studies suggested a possible link with lung cancer, mainly in people who also smoked, and could not establish cause.How often is not known
- LimitedCase reports: US poison centers recorded 8,269 liquid nicotine exposures in children under 6 from 2012 to 2017, mostly by swallowing.How often is not known
What it was studied for, and what was found
Shown to help6
Quitting smoking, against nicotine replacement
Shown to help more people stop smoking for at least 6 months than nicotine replacement therapy, about 4 more quitters per 100, in high-certainty pooled trials.
Compared with nicotine replacement therapy [1]; conventional quit treatments, nicotine replacement or behavioral [2]; nicotine replacement therapy, across 14 reviews [3]; nicotine replacement therapy, in the largest single trial [4]
The numbers and sources
- Effect
- Nicotine e-cigarettes raised quit rates against nicotine replacement therapy (RR 1.61, 95% CI 1.23 to 2.12, 11 studies, high-certainty evidence), about 4 more quitters per 100 (95% CI 1 to 7) [1]. A second meta-analysis found more biochemically confirmed abstinence than with conventional quit treatments (RR 1.77, 95% CI 1.29 to 2.44) [2]. Across 14 reviews, every pooled estimate favored nicotine e-cigarettes, with ratios typically 1.17 to 1.67 against nicotine replacement [3]. In the largest single trial, 1-year abstinence was 18.0% with e-cigarettes and 9.9% with nicotine replacement (RR 1.83, 95% CI 1.30 to 2.58), both with weekly behavioral support [4].
- Population
- 4,114 adults who smoked in 11 randomized trials, from 80 trials with 29,861 participants in all [1]. 3,253 adults in 5 trials of at least 6 months [2]. 14 reviews [3]. 886 adults at UK stop-smoking services [4].
- Sources
- [1], [2], [3], [4]
- Caveats
- The trials tested regulated nicotine e-cigarettes. Illicit products or products with other substances such as THC may differ [1]. Heterogeneity was moderate (I² 55%) [1]. Most trials were in high-income countries [3].
Quitting smoking, against e-cigarettes without nicotine
Shown to help more people stop smoking than e-cigarettes without nicotine, about 2 more quitters per 100, in two meta-analyses of randomized trials.
Compared with e-cigarettes without nicotine [1][2]; non-nicotine e-cigarettes or placebo, across 14 reviews [3]
The numbers and sources
- Effect
- Nicotine e-cigarettes probably raised quit rates against e-cigarettes without nicotine (RR 1.34, 95% CI 1.05 to 1.69, 7 studies, moderate-certainty evidence), about 2 more quitters per 100 [1]. A second review found an RR of 1.56 (95% CI 1.13 to 2.15) [2]. Across 14 reviews, ratios against non-nicotine e-cigarettes typically ran 1.46 to 2.09 [3].
- Population
- 1,918 adults in 7 trials [1]. Adults in 5 trials of at least 6 months [2]. 14 reviews [3].
- Sources
- [1], [2], [3]
- Caveats
- Evidence was downgraded for imprecision [1]. The two meta-analyses draw on overlapping trials, so their agreement is not fully independent.
Quitting smoking, against behavioral support or no support
Shown to help more people stop smoking than behavioral support alone or no support, in pooled trials rated low in certainty because of risk of bias.
Compared with behavioral support only or no support [1]
The numbers and sources
- Effect
- Quit rates were higher with nicotine e-cigarettes than with behavioral support only or no support (RR 1.75, 95% CI 1.39 to 2.20, 11 studies, low-certainty evidence) [1].
- Population
- 7,214 adults who smoked in 11 trials [1].
- Sources
- [1]
- Caveats
- People in these trials knew whether they were given a device, and the review rated the evidence low in certainty for that reason [1].
Exposure markers after switching from cigarettes
Shown to lower exhaled carbon monoxide and most measured markers of potential harm in people who switched fully from cigarettes to e-cigarettes in quit trials.
Compared with people who kept smoking cigarettes [5]; dual users of e-cigarettes and cigarettes [5]
The numbers and sources
- Effect
- Exhaled carbon monoxide was 9.57 ppm lower in people using only e-cigarettes than in people who kept smoking (95% CI -17.30 to -1.83, 3 studies). Against continued smoking, 12 of 13 markers of potential harm were significantly lower in e-cigarette users, with no difference in the 13th. Against dual users, 12 of 25 markers were lower in e-cigarette users and 5 were lower in dual users [5].
- Population
- 1,299 adults who smoked and were given e-cigarettes in 9 studies in Greece, Italy, Poland, the UK and the US [5].
- Sources
- [5]
- Caveats
- People chose whether to switch fully, so the groups were not randomized against each other. Only one study had data on people who used neither product [5]. Lower exposure markers do not show lower disease.
Blood vessel function after switching
One trial found better blood vessel function within 1 month in smokers who switched to e-cigarettes, with or without nicotine, than in those who kept smoking.
Compared with people who kept smoking, a nonrandomized preference group [6]
The numbers and sources
- Effect
- Within 1 month of switching, flow-mediated dilation improved by 1.49% (95% CI 0.93 to 2.04) against continued smoking, and arterial stiffness fell (pulse wave velocity -0.529 m/s, 95% CI -0.946 to -0.112). Women gained more than men. E-cigarettes with and without nicotine did not differ [6].
- Population
- Adults smoking at least 15 cigarettes a day for at least 2 years, free of heart disease, randomized to e-cigarettes with or without nicotine, with a smoking comparison group [6].
- Sources
- [6]
- Caveats
- The comparison with continued smoking was not randomized and was adjusted by propensity score. Follow-up was 1 month [6].
Cough and phlegm after switching
One trial found cough and phlegm fell more over a year with e-cigarettes than with nicotine replacement, with no difference in wheezing or shortness of breath.
Compared with nicotine replacement therapy [4]
The numbers and sources
- Effect
- From baseline to 52 weeks, the e-cigarette group had greater declines in cough (RR 0.8, 95% CI 0.6 to 0.9) and phlegm (RR 0.7, 95% CI 0.6 to 0.9) than the nicotine replacement group. Wheezing and shortness of breath did not differ [4].
- Population
- 886 adults at UK stop-smoking services [4].
- Sources
- [4]
- Caveats
- Symptoms were self-reported and participants knew their group. Part of the difference may come from more people quitting cigarettes in the e-cigarette group [4].
Amounts studied
The quit trials gave adults who smoked a nicotine e-cigarette and measured abstinence from smoking at 6 months or more [1]. The largest trial gave a refillable second-generation device with one bottle of 18 mg/mL nicotine e-liquid and weekly behavioral support for at least 4 weeks. Its comparison group chose nicotine replacement products for up to 3 months [4]. The vascular trial switched smokers of at least 15 cigarettes a day to e-cigarettes with or without nicotine for 1 month [6]. Studies of heart rate and blood pressure measured acute effects of single vaping sessions [7]. Population studies compared ever, current or past-30-day e-cigarette use with no use [8][9][10].
Risks
Reported risks8
Continued vaping after quitting smoking
One trial found 80% of people who quit with e-cigarettes were still vaping a year later, against 9% still using nicotine replacement.
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- Among people abstinent from smoking at 1 year, 80% (63 of 79) in the e-cigarette group were still using their e-cigarette at 52 weeks, against 9% (4 of 44) in the nicotine replacement group still using it [4].
- Population
- 886 adults at UK stop-smoking services [4].
- Sources
- [4]
- Caveats
- One trial. What years of continued vaping do to health is not known from these trials [1].
Throat and mouth irritation and other minor effects in quit trials
One trial found throat or mouth irritation in 65% of e-cigarette users against 51% with nicotine replacement. Pooled trials found overall adverse events similar to nicotine replacement.
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- Throat or mouth irritation was reported by 65.3% in the e-cigarette group and 51.2% with nicotine replacement. Nausea was more common with nicotine replacement (37.9% against 31.3%) [4]. In pooled trials, adverse events were similar against nicotine replacement (RR 0.95, 95% CI 0.72 to 1.24, low certainty) and against e-cigarettes without nicotine (RR 1.01). Against behavioral support or no support they may be more common (RR 1.22, 95% CI 1.00 to 1.49, very low certainty) [1].
- Population
- 886 adults [4]. 3,107 adults in 8 trials, 909 in 6 trials and 2,801 in 11 trials [1].
- Sources
- [4], [1]
- Caveats
- Pooled adverse event estimates were imprecise and inconsistent [1].
Later cigarette smoking in young people
Linked to three to four times the odds of later starting to smoke in young people who had vaped, in two meta-analyses of longitudinal studies.
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- In young people who had never smoked, 30.4% of those who had used e-cigarettes started smoking, against 7.9% of those who had not (adjusted OR 3.62, 95% CI 2.42 to 5.41). Past-30-day vaping was linked to past-30-day smoking at follow-up (OR 4.28) [9]. A second review found an OR of 4.59 (95% CI 3.60 to 5.85), with high heterogeneity (I² 88%) [10].
- Population
- 17,389 adolescents and young adults aged 14 to 30 in 9 studies [9]. 17 studies of young people up to 30 [10].
- Sources
- [9], [10]
- Caveats
- Observational. Young people who try e-cigarettes may differ in ways that also lead to smoking. Smoking was self-reported, and no study used negative controls that could test whether the link is causal [10].
Short-term rises in heart rate and blood pressure
Shown to raise heart rate and blood pressure slightly right after vaping, in one meta-analysis of 14 short studies.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Acute vaping raised heart rate by 2.27 beats a minute (95% CI 1.64 to 2.89), diastolic pressure by 2.01 mmHg (95% CI 0.62 to 3.39) and systolic pressure by 2.02 mmHg (95% CI 0.07 to 3.97). The review also reported lower blood pressure in people who switched from smoking to long-term vaping. Effects on endothelial function and arterial stiffness came from single studies [7].
- Population
- 441 participants in 14 studies [7].
- Sources
- [7]
- Caveats
- Mostly non-randomized studies of moderate quality. Acute changes do not show long-term heart disease [7].
Asthma and COPD
Linked to more asthma and COPD in people who vape, after accounting for cigarette smoking, in one meta-analysis of population studies.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- E-cigarette use was linked to asthma (adjusted OR 1.39, 95% CI 1.28 to 1.51, 15 studies) and COPD (adjusted OR 1.49, 95% CI 1.36 to 1.65, 9 studies), controlling for cigarette smoking and other factors [8].
- Population
- General-population samples in 15 asthma studies and 9 COPD studies, cross-sectional and longitudinal [8].
- Sources
- [8]
- Caveats
- Observational, with many cross-sectional studies, so the order of events is unclear. People with lung disease may switch from cigarettes to e-cigarettes, which is reverse causation, and past smoking is hard to account for fully.
Vaping-associated lung injury (EVALI)
Case series: a US outbreak of lung injury in 2019 and 2020 hospitalized 2,668 people, mostly users of THC vaping products, with vitamin E acetate found in most cases tested.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- By January 14, 2020, 2,668 hospitalized cases had been reported, median age 24 and 66% male. 82% reported using THC-containing products and 14% only nicotine-containing products [11]. Vitamin E acetate was found in lung fluid from 48 of 51 patients (94%) and in none of 99 healthy comparators [12].
- Population
- US patients hospitalized with EVALI, August 2019 to January 2020 [11]. 51 patients in 16 states and 99 comparators [12].
- Sources
- [11], [12]
- Caveats
- Case counts with no denominator of users. CDC stated that other chemicals in THC or non-THC products could not be ruled out in some cases [11].
Lung cancer
Limited evidence: a review of five observational studies suggested a possible link with lung cancer, mainly in people who also smoked, and could not establish cause.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Five observational studies, published 2019 to 2024, suggested a potential association between e-cigarette use and lung cancer, with the highest likelihood in people who used both cigarettes and e-cigarettes [13].
- Population
- 5 studies with 3,162 to 4,329,288 participants [13].
- Sources
- [13]
- Caveats
- Heterogeneous studies with little long-term data. Most users had also smoked, and cancer takes decades to develop [13].
Nicotine poisoning in young children
Case reports: US poison centers recorded 8,269 liquid nicotine exposures in children under 6 from 2012 to 2017, mostly by swallowing.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- 92.5% of exposures were by ingestion and 83.9% involved children under 3. 35.1% were treated and released from a health care facility and 1.4% were admitted. The yearly rate rose from 0.7 to 10.4 per 100,000 children from 2012 to 2015, then fell to 8.3 in 2016, after a federal child-resistant packaging law [14].
- Population
- Children under 6 reported to the US National Poison Data System, January 2012 to April 2017 [14].
- Sources
- [14]
- Caveats
- Poison center reports undercount exposures and give no rate per household with e-liquid.
Checked, no increase found1
Serious adverse events in quit trials
Not shown to raise serious adverse events against nicotine replacement in pooled trials, with short follow-up and some reviews unable to rule out a rise.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Serious adverse events were probably similar with nicotine e-cigarettes and nicotine replacement (risk difference 0.01, 95% CI -0.01 to 0.02, 10 studies, moderate certainty) and similar against e-cigarettes without nicotine (RD 0.00). Evidence against behavioral support or no support was insufficient to judge [1]. Of 13 reviews that pooled serious adverse events, two found point estimates suggesting more with nicotine e-cigarettes, and the rest included no difference [3].
- Population
- 4,045 adults in 10 trials, 1,786 in 11 trials and 5,032 in 18 trials [1]. 13 reviews [3].
- Sources
- [1], [3]
- Caveats
- The authors state that longer, larger trials are needed to fully evaluate harms [1]. An overview of reviews called the serious adverse event evidence inconclusive [3].
Claims tested and not found
- That e-cigarettes help no more people quit than nicotine replacement. Pooled trials found more quitters with nicotine e-cigarettes (RR 1.61, high certainty) [1].
- That the quit effect comes only from the hand-to-mouth habit, not the nicotine. Nicotine e-cigarettes led to more quitters than e-cigarettes without nicotine (RR 1.34) [1][2].
- That e-cigarettes in quit trials cause more serious adverse events than nicotine replacement. Rates were probably similar (risk difference 0.01, 95% CI -0.01 to 0.02) [1].
Related
Sources
- Lindson N, Livingstone-Banks J, Butler AR, et al. Electronic cigarettes for smoking cessation. Cochrane Database of Systematic Reviews. 2026. https://doi.org/10.1002/14651858.CD010216.pub11
- Levett JY, Filion KB, Reynier P, Prell C, Eisenberg MJ. Efficacy and Safety of E-Cigarette Use for Smoking Cessation: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. The American Journal of Medicine. 2023. https://doi.org/10.1016/j.amjmed.2023.04.014
- Wu AD, Conde M, Butler AR, et al. Electronic cigarettes for smoking cessation: An overview of systematic reviews and evidence and gap map. Addiction. 2026. https://doi.org/10.1111/add.70388
- Hajek P, Phillips-Waller A, Przulj D, et al. A Randomized Trial of E-Cigarettes versus Nicotine-Replacement Therapy. New England Journal of Medicine. 2019. https://doi.org/10.1056/NEJMoa1808779
- Hartmann-Boyce J, Butler AR, Theodoulou A, et al. Biomarkers of potential harm in people switching from smoking tobacco to exclusive e-cigarette use, dual use or abstinence: secondary analysis of Cochrane systematic review of trials of e-cigarettes for smoking cessation. Addiction. 2023. https://doi.org/10.1111/add.16063
- George J, Hussain M, Vadiveloo T, et al. Cardiovascular Effects of Switching From Tobacco Cigarettes to Electronic Cigarettes. Journal of the American College of Cardiology. 2019. https://doi.org/10.1016/j.jacc.2019.09.067
- Skotsimara G, Antonopoulos AS, Oikonomou E, et al. Cardiovascular effects of electronic cigarettes: A systematic review and meta-analysis. European Journal of Preventive Cardiology. 2019. https://doi.org/10.1177/2047487319832975
- Wills TA, Soneji SS, Choi K, Jaspers I, Tam EK. E-cigarette use and respiratory disorders: an integrative review of converging evidence from epidemiological and laboratory studies. European Respiratory Journal. 2021. https://doi.org/10.1183/13993003.01815-2019
- Soneji S, Barrington-Trimis JL, Wills TA, et al. Association Between Initial Use of e-Cigarettes and Subsequent Cigarette Smoking Among Adolescents and Young Adults: A Systematic Review and Meta-analysis. JAMA Pediatrics. 2017. https://doi.org/10.1001/jamapediatrics.2017.1488
- Khouja JN, Suddell SF, Peters SE, Taylor AE, Munafò MR. Is e-cigarette use in non-smoking young adults associated with later smoking? A systematic review and meta-analysis. Tobacco Control. 2020. https://doi.org/10.1136/tobaccocontrol-2019-055433
- Krishnasamy VP, Hallowell BD, Ko JY, et al. Update: Characteristics of a Nationwide Outbreak of E-cigarette, or Vaping, Product Use-Associated Lung Injury, United States, August 2019 to January 2020. MMWR Morbidity and Mortality Weekly Report. 2020. https://doi.org/10.15585/mmwr.mm6903e2
- Blount BC, Karwowski MP, Shields PG, et al. Vitamin E Acetate in Bronchoalveolar-Lavage Fluid Associated with EVALI. New England Journal of Medicine. 2020. https://doi.org/10.1056/NEJMoa1916433
- Mohapatra S, Tiwari A, Kandala A, et al. The risk of lung cancer from vaping or e-cigarette usage: a systematic review. ESMO Open. 2025. https://doi.org/10.1016/j.esmoop.2025.105910
- Govindarajan P, Spiller HA, Casavant MJ, Chounthirath T, Smith GA. E-Cigarette and Liquid Nicotine Exposures Among Young Children. Pediatrics. 2018. https://doi.org/10.1542/peds.2017-3361