Published by the Cochrane Collaboration in 2024 and updated as a living review, this systematic review included 88 completed studies representing 27,235 participants, of which 47 were randomized controlled trials.

The review found high-certainty evidence that nicotine e-cigarettes increase smoking quit rates compared to traditional nicotine replacement therapy like patches or gum. The pooled risk ratio was 1.59, meaning e-cigarette users were 59% more likely to quit. In absolute terms, if 6 people out of 100 quit using nicotine replacement therapy, between 8 and 12 people out of 100 would quit using nicotine e-cigarettes.

There was also moderate-certainty evidence that nicotine e-cigarettes increase quit rates compared to e-cigarettes without nicotine, and low-certainty evidence they may increase quit rates compared to behavioral support alone. The review did not find evidence of serious harms from nicotine e-cigarettes when used for quitting, though long-term data beyond two years remains limited.

Published in The American Journal of Medicine in 2023, this systematic review and meta-analysis followed PRISMA guidelines and included only randomized controlled trials comparing nicotine e-cigarettes to other cessation methods.

The analysis pooled data from over 3,200 participants and found a robust benefit at longer-term follow-up (6 months or more) for nicotine e-cigarettes in increasing smoking abstinence. E-cigarettes were more effective than both conventional nicotine replacement therapies (patches, gum, lozenges) and behavioral counseling alone.

The authors concluded that among individuals attempting to quit smoking, nicotine e-cigarettes are more efficacious than conventional nicotine replacement or behavioral smoking cessation therapies, and may prove beneficial in reducing smoking-related health risks by helping smokers transition away from combustible cigarettes.

Published in Drug and Alcohol Dependence in 2024, this critical umbrella review analyzed systematic reviews of the highest methodological quality on e-cigarettes for smoking cessation. Eight systematic reviews rated as moderate or high confidence were included, covering 24 randomized controlled trials.

In 8 out of 11 direct comparisons across these reviews, e-cigarettes were found to be more effective than the comparison treatment for achieving smoking cessation. The absolute success rates for quitting with e-cigarettes ranged from 10% to 12% at 6 months to one year of follow-up.

While these quit rates may seem modest, they compare favorably to other cessation aids. The reviewers noted that the evidence base has grown substantially in recent years, with the certainty of evidence improving from low to high for the comparison against nicotine replacement therapy.

Published in the New England Journal of Medicine in 2019, this landmark randomized controlled trial was conducted across NHS stop-smoking services in the United Kingdom. It enrolled 886 adult smokers who wanted to quit and randomly assigned them to either an e-cigarette starter pack or their choice of nicotine replacement therapy (patches, gum, lozenges, or combinations).

At the one-year follow-up, 18.0% of participants in the e-cigarette group were confirmed abstinent from smoking, compared to 9.9% in the nicotine replacement therapy group. This means e-cigarette users were about 80% more likely to have quit (relative risk 1.83). Both groups received weekly behavioral support for at least four weeks.

Among those who had not quit entirely, participants in the e-cigarette group showed a greater reduction in the number of cigarettes smoked per day. However, 80% of the e-cigarette group was still using e-cigarettes at one year, compared to only 9% still using nicotine replacement products.

Published in BMC Public Health in 2020, this evaluation covered an NHS pilot scheme run in a socially deprived area of North West England that encouraged smokers to swap from conventional cigarettes to e-cigarettes by providing free e-cigarette starter kits, liquid, and behavioral support.

Of the 1,022 participants who enrolled, 614 remained engaged at 4 weeks. Among those still engaged, 62% had quit smoking entirely. Overall, 37% of all enrolled participants (381 people) were confirmed to be using only an e-cigarette and no longer smoking at follow-up.

The pilot demonstrated that for every five people entering the scheme, three stayed on the program and reduced their cigarette smoking, and one cut out cigarettes completely. This success has informed the broader national NHS Swap to Stop program, which aims to provide one million smokers with free vape starter kits and behavioral support.

Published in Frontiers in Public Health in 2024, this systematic review and network meta-analysis compared the efficacy and acceptability of multiple smoking cessation interventions including various pharmacological treatments and e-cigarettes.

The network meta-analysis allows indirect comparisons between treatments that may not have been tested head-to-head in the same trial. E-cigarettes with nicotine ranked among the most effective interventions for achieving verified smoking abstinence at 6 months or longer.

The analysis also examined acceptability, meaning how likely participants were to continue using the assigned treatment. E-cigarettes showed favorable acceptability compared to pharmacological alternatives, which is important because a cessation aid only works if people actually use it consistently.

Published in the British Medical Journal in 2017, researchers at the University of California San Diego analyzed data from the US Census Current Population Survey Tobacco Use Supplement (CPS-TUS), a nationally representative survey of adults aged 18 and older.

The study examined over 160,000 respondents and found that 65% of smokers who used e-cigarettes within the previous 12 months had attempted to quit smoking, compared to 40% of smokers who did not use e-cigarettes. The overall population cigarette quit rate increased from 4.5% in 2010-2011 to 5.6% in 2014-2015, coinciding with the rapid rise in e-cigarette availability.

The researchers calculated that the increase represented about 350,000 additional quitters nationally during the period when e-cigarette use became widespread. While the study is observational and cannot prove causation, the timing and magnitude of the increase in quit attempts and successful quits aligned with e-cigarette market growth.

Published in the New England Journal of Medicine in 2024, this editorial by leading tobacco researchers examined whether the accumulating evidence on e-cigarettes for smoking cessation has reached a critical threshold for clinical and policy acceptance.

The editorial highlighted that the Cochrane review now rates the evidence as high-certainty for the superiority of nicotine e-cigarettes over nicotine replacement therapy, a significant upgrade from the uncertain evidence of just a few years prior. The authors noted this represents a potential "tipping point" in the scientific consensus.

The piece acknowledged that regulatory environments in the US and UK have diverged significantly, with the UK embracing e-cigarettes as a cessation tool through programs like Swap to Stop, while the US FDA has taken a more cautious approach. The authors argued that clinicians should discuss e-cigarettes with patients who have failed other quit methods.

Published by Public Health England (now the Office for Health Improvement and Disparities) in 2015 and updated in 2018, this independent evidence review was conducted by a team of leading tobacco researchers to assess the health risks and cessation potential of e-cigarettes.

The review concluded that based on the available evidence, e-cigarettes are around 95% less harmful than smoking combustible cigarettes. This estimate was based on the much lower levels of toxicants measured in e-cigarette vapor compared to cigarette smoke, though it acknowledged this is not the same as saying e-cigarettes are safe.

The review found that e-cigarettes could be an effective tool for smoking cessation, particularly when combined with behavioral support from stop-smoking services. The UK subsequently became the first country to formally integrate e-cigarettes into its national cessation strategy, a policy now backed by the NHS Swap to Stop program.

Published in 2025 as the latest update to the Cochrane living systematic review on electronic cigarettes for smoking cessation, this version expanded the evidence base to include over 100 studies and additional randomized controlled trials.

The core finding remained consistent with previous updates: there is high-certainty evidence that nicotine e-cigarettes increase quit rates compared to traditional nicotine replacement therapy. The risk ratio remained similar to the 2024 update, confirming the robustness of this finding across multiple independent trials in different countries and settings.

The living review format means the Cochrane team continuously monitors new trials and updates the analysis as relevant data emerges. The consistency of findings across successive updates strengthens confidence that the observed benefit is real and not a statistical artifact of any single trial. Safety data continued to show no serious adverse events attributable to nicotine e-cigarettes in the cessation context.