AMSTERDAM — At the European Respiratory Society (ERS) Congress 2025, respiratory experts lay out the pros and cons of using e-cigarettes in smoking cessation. While some clinicians champion the devices as a crucial harm-reduction tool, others argue there is insufficient evidence to justify their use and point to a growing list of public health concerns. Meanwhile, researchers presented promising data on novel cessation therapies.

“I think there is strong evidence that e-cigarettes can help people stop smoking,” said Hayden McRobbie, PhD, a professor of public health at Queen Mary University of London, London, England, who argued that actively deterring smokers from switching to a less harmful alternative is not the right approach.

However, Aslı Görek Dilektaşlı, MD, an associate professor at the Department of Pulmonary Medicine at Uludag University, Bursa, Turkey, warned against accepting these products as a valid aid for quitting. “When 80% of the e-cigarette group remains dependent on e-cigarettes, we can’t talk about smoking cessation,” she argued. “It’s not cessation. It’s a product switch.”

The Case for Harm Reduction

McRobbie recognized that smoked tobacco is one of the worst public health enemies. It shortens life expectancy by 10 years, and it’s responsible for around 8 million deaths per annum globally. And although global tobacco use has been steadily declining for decades, “the problem has not gone away,” he said.

Data from 2023 showed high smoking rates among several European countries, and almost half of these current smokers are smoking between half and a whole pack a day. Over time, this behavior causes a rapid decline in lung function, but stopping smoking reduces that, McRobbie explained. “[It’s] never too late to stop smoking.”

Given this context, he positioned e-cigarettes as a pragmatic tool for harm reduction by presenting evidence from a Cochrane review of several high-quality randomized controlled trials, which, he said, shows with high certainty that nicotine-containing e-cigarettes are more effective for smoking cessation at 12 months than traditional nicotine replacement therapy (NRT).

To illustrate the real-world impact of these findings, he presented a randomized controlled trial conducted in Australia that focused on people from lower socioeconomic groups. This demographic often smokes more and faces greater challenges in quitting. Even in this difficult-to-treat population, e-cigarettes proved more effective than NRT products like gum or lozenges in achieving biochemically validated abstinence.

Yet McRobbie stressed that e-cigarettes are “less harmful than tobacco but not harmless,” making a clear distinction that while “switching is good, starting it isn’t.”

He advocated for a carefully managed harm-reduction strategy, with the ultimate goal to help people stop using both tobacco and nicotine, but “the majority of problems come from tobacco rather than nicotine,” he said. “Should we help people stop tobacco first?” He called for a regulatory framework where e-cigarettes are made accessible to adult smokers who want to quit but are simultaneously restricted for nonsmokers, particularly young people.

A Cascade of New Risks 

According to Dilektaşlı, however, e-cigarettes do not solve the problem of nicotine addiction but merely change its form. She pointed out that while NRT is a time-limited therapy, vaping often becomes a continuous, long-term behavior, which in itself is a public health hazard. “Smoking rates were declining, and this decline was achieved without electronic cigarettes. And this decline is not accelerated by electronic cigarettes.”

Dilektaşlı critiqued the methodology of studies that support the efficacy of e-cigarettes, arguing that they suffer from a comparative bias. For example, she said that in some trials, the e-cigarette group was allowed to choose their own devices and flavors, while the NRT group received a fixed supply of a single product, creating an unfair advantage that favored the e-cigarette group.

She warned that the focus on replacing tobacco overlooks the inherent dangers of sustained nicotine use. “Nicotine is not harmless by itself,” she said. She explained that it is linked to addiction, cardiovascular strain, metabolic disturbances, cancer, neurological issues, renal, and cardiac fibrosis. And a large Korean study found that ex-smokers who vape have a 2.7 times higher risk of developing lung cancer than ex-smokers who do not. Added to this are the cytotoxic effects of thousands of chemical flavorings and the physical danger of device explosions.

The VapeScan study, presented at ERS 2025 by Elizabeth Oelsner, MD, DrPH, a general internist and respiratory epidemiologist, and associate professor of Medicine at Columbia University in New York City, found that healthy young adults who are dual users of cigarettes and e-cigarettes have significantly lower pulmonary microvascular perfusion. This is a concerning finding, as these vascular changes are typically seen in older adults with chronic obstructive pulmonary disease.

Mechanistic studies are also beginning to explain how this damage occurs. Research by Kerry Arrowsmith, a PhD candidate in the Faculty of Medical and Health Sciences, Te Kupenga Hauora Māori, University of Auckland, Auckland, New Zealand, utilized computational models to demonstrate that vaping can impair lung surfactants. An e-cigarette works by heating a liquid — which contains propylene glycol, vegetable glycerin, flavorings, and nicotine — to create an aerosol. This aerosol, when inhaled, can damage the surfactant layer that lines the alveoli, making the lungs “stiffer” and requiring “higher pressure to inflate.” Her team’s in vitro work exposing alveolar epithelial cells to vape aerosol also revealed that various e-liquid components — not just nicotine — were cytotoxic and disrupted the crucial cell barrier.

The risks extend beyond the individual user to the entire population, Dilektaşlı explained. She presented evidence of a “gateway effect,” where youth who use e-cigarettes have a significantly higher risk of starting to smoke traditional cigarettes. She also highlighted the dangers of dual use, which increases the likelihood of continued smoking and the increased risk for relapse among former smokers who take up vaping.

One Promising Alternative

Massimiliano Cani, MD, a medical oncologist and a PhD candidate at the University of Turin, Turin, Italy, presented a study that looked at cytisine, a low-cost, plant-based alkaloid that acts as a partial agonist at nicotinic acetylcholine receptors, as a potential aid to support smokers to quit. The study compared the quit rates of participants who received counseling alone with those who received counseling plus a course of cytisine.

The results were promising, with the group receiving the combination of cytisine and counseling achieving a smoking cessation rate of approximately 50%. “Our findings show that the combination was a safe and highly effective intervention,” Cani said. He added that the drug was generally well-tolerated, with side effects such as mild gastrointestinal issues and insomnia, consistent with what has been previously reported in the literature. While in countries like Italy, cytisine is not approved for this purpose, it can be purchased in pharmacies as a prepared medicine. In other countries, such as Poland, cytisine can be bought over the counter.

A Lesson From History

For now, the official stance of the respiratory expert community remains cautious. Stamatoula Tsikrika, MD, medical doctor at Evangelismos Hospital, Athens, Greece, said the European Respiratory Society “does not endorse novel tobacco products or nicotine products, including e-cigarettes, as a safe and effective tool for tobacco cessation.”

Dilektaşlı said that the promotion of these devices plays directly into the hands of the tobacco industry and serves to “renormalize the act of smoking.” She drew a historical parallel, reminding the audience of a time when physicians were featured in advertisements promoting the safety of certain cigarette brands. “Do we really want to be recalled by our future colleagues in the same way?”

McRobbie, Dilektaşlı, Oelsner, Arrowsmith, Cani, and Tsikrika reported no relevant financial relationships.

Manuela Callari is a freelance science journalist specializing in human and planetary health. Her work has been published in The Medical Republic, Rare Disease Advisor, New Scientist, The Guardian, MIT Technology Review, and others.