For more than a decade, electronic cigarettes were promoted as a “much safer” alternative to combustible cigarettes. First, it was claimed they were “95% less harmful” based on expert opinion. Later, some narratives based on regulatory and communication interpretations derived from the “modified risk tobacco product” (MRTP) framework used by the U.S. Food and Drug Administration (FDA) placed the harm caused by these products at between 10% and 20% of that of combustible cigarettes. These claims became embedded in public debate, influenced regulations, and were used to justify promoting them as a harm-reduction strategy.
However, the most up-to-date scientific evidence is changing the picture again.
A recent meta-analysis published in Public Health Reports, the official journal of the Office of the U.S. Surgeon General, titled “Comparison of e-Cigarette and Cigarette Use and Dual Use Associations with Disease: Updated Systematic Review and Meta-Analysis,” analyzed 124 studies that assessed diagnosed disease in e-cigarette users, smokers, and dual users.
The results are clear: e-cigarettes are far from harmless, and, for several major conditions, the risk is very close to that of combustible cigarettes.
Beyond biomarkers: real disease
One of the most relevant aspects of the study is that it does not focus only on toxic exposure or intermediate biomarkers but on clinically diagnosed disease. This represents a fundamental advance in the debate, which for years relied on partial chemical comparisons of aerosol versus smoke.
The analysis shows that:
- For metabolic dysfunction and oral disease, there is no detectable difference in risk between current e-cigarette users and smokers.
- For cardiovascular disease (OR = 0.76), stroke (OR = 0.62), asthma (OR = 0.84), COPD (OR = 0.55), and fetal growth (OR = 0.62, low confidence), the risk is lower than that of combustible cigarettes but far higher than the 5% or 15% relative harm that has been widely promoted publicly.
In other words, even if the harm is not identical to that of combustible cigarettes, electronic devices are nowhere near being “95% less harmful.” The true magnitude of the risk is several times higher than the figures suggest.
The bigger problem: dual use
A particularly concerning finding is the impact of dual use (simultaneous use of e-cigarettes and combustible cigarettes). According to the meta-analysis, the disease risk associated with dual use is higher than exclusive smoking for nearly all outcomes studied, except fetal growth.
This has direct implications for health policy. Numerous studies show that for every smoker who completely quits cigarettes through the use of e-cigarettes, between two and four end up in a dual-use pattern. If dual use increases risk, the population-level balance could be negative.
The promise of “harm reduction” through e-cigarette use could, in practice, translate into a future with disease and death levels not very different from current ones while the industry manages to delay regulations and maintain its profits.
People who never smoked: an unnecessary risk
The analysis also documents that e-cigarette use among people who never smoked is associated with higher disease risk compared with non-users:
- 24% higher risk of cardiovascular disease
- 45% higher risk of COPD
- 53% higher risk of oral disease
These data are especially relevant in the context of the expanding use of these products among adolescents and young adults who had never used combustible tobacco.
Harm reduction or redefining harm?
The concept of harm reduction implies a substantial, proven decrease in harm at both the individual and population levels. To sustain that category, the benefit must be clear, consistent, and clinically meaningful.
Current evidence does not support that e-cigarettes meet this criterion:
- The risk for several diseases is close to that of combustible cigarettes.
- Dual use may worsen the risk profile.
- The addition of new users (especially young people) expands the exposed population base.
Although long-term follow-up is still needed, as with any relatively new product, the volume of accumulated evidence, especially studies published from 2020 onward (81% of the total analyzed), already provides robust signals.
A necessary conclusion
The widely circulated claims that e-cigarettes are “95% less harmful” derived from the 2015 Public Health England report or that they cause only “10–20% of the harm” of combustible cigarettes were based on expert estimates and comparisons of toxic exposure, not clinical disease outcomes.
In contrast, the most recent epidemiological evidence based on diagnosed disease, presented in the article discussed here, shows odds ratios (ORs) substantially higher than what those figures would imply.
The updated meta-analysis shows values indicating modest relative reductions, not 80–95%, and for some outcomes, no detectable differences were observed. In addition, dual use showed risks equal to or greater than exclusive smoking for most pathologies.
Consequently, comparing hypothetical low-harm estimates (5–20%) with the observed ORs in clinical disease suggests that the initial claims of substantial harm reduction do not hold up in light of current epidemiological evidence.
The debate about e-cigarettes cannot continue to rely on hypothetical estimates or partial toxicological comparisons. The relevant question is: what happens to real disease?
The answer, according to this updated systematic review, is clear: e-cigarettes are not harmless, not minimally harmful, and cannot be presented as a significant reduction in harm at the population level. For several major conditions, risk is close to that of combustible cigarettes, and dual use could be even worse.
In public health, decisions must be based on the best available evidence, not slogans. And today, growing evidence indicates that the harm-reduction narrative around these products does not hold.
The challenge now is to align communication, regulation, and clinical practice with this scientific reality.