The articles I saw (years ago) claimed that vaping was a gateway to smoking, but the data showed that vaping just replaced smoking for teens. That is, once e-cigs became available, the same amount of teens were doing one or the other, but more were using e-cigs than cigarettes. So, if the amount of teens doing one or the other remained stable, but e-cig use largely replaced cigarette use, I think you have to consider the teens using the e-cigs. If you removed e-cigs as an option, would they smoke cigarettes or abstain altogether? It seems to me that they'd be more likely (as a group) to smoke cigarettes.
Disclaimer: I switched from smoking to vaping in 2013 and haven't smoked a cigarette since. I use unflavored e-liquid for a few reasons, but, as I understand it, inhaling flavorings meant to be ingested is the primary health risk with vaping. Last I checked, this issue was still under debate.
I would be surprised to see that inhaling any kind of smoke or non-water aerosol is good for your lungs, so I'd expect at least a minor harmful effect.
This study, for example, claims increased risks for heart disease [1] (disclaimer: I'm not a medical doctor and cannot evaluate its credibility)
[1] https://link.springer.com/article/10.1007/s40138-020-00219-0
However, by comparison, tobacco smoke is like "what if we could engineer the perfect lung assailant."
Tar causes inflammation, damages DNA directly, intercalates DNA and induces replication errors, collapses alveoli, and paralyzes cillia, making clearance of all those chemical assailants from the lungs even harder.
You want to classify sugar as harmful? It's physiologically addictive (go a few days without carbs altogether and tell us how it goes).
What about caffeine?
Caffeine is also addictive and if you drink enough, stopping gives you withdrawal headaches. But in my experience not drinking caffeine at all makes me just as alert as getting used to the daily dose I thought I needed before.
So yeah, I'd totally classify both as slightly harmful.
But some harmful things are worth the tradeoff if you can maintain a low enough dose (sugar or caffeine)
Vaping might have social and physiological benefits which outweigh the harm also.
Even the physical addictiveness of nicotine is not that strong when separated from the rituals of smoking compared to e.g. caffeine (where addiction is also massively affected by rituals).
https://en.m.wikipedia.org/wiki/Nicotine
> Nicotine is classified as a poison. However, at doses used by consumers, it presents little if any hazard to the user.
That aside, the collective balance is: - how many cigarette smokers will switch (benefit)
- how many people will start vaping instead of smoking (benefit)
- how many people will switch from vaping to smoking (harm)
- how many people will start vaping but wouldn't have started smoking (harm)
Perhaps someone with expertise can explain the current state of research. IIRC I saw a study arguing that the beneficial effects were less frequent and vaping as an entry to smoking was shockingly prevalent.