You are conflating the harms of the delivery mechanism with the harms of the substance.

Nicotine gum is relatively harmless for example. Or perhaps imbibe on a Nicotini[0]?

[0] https://en.wikipedia.org/wiki/Nicotini

You're right that these studies measure the product, not the substance. But TFA is about vaping, and I am referring to that.

[edit] Seems that nicotine is not really harmless, even in gum or patches: double the risk of heart palpitations and chest pains, 1.67 the risk of nausea and vomiting, 1.5 times the risk of gastrointestinal complaints, and 1.4 times the risk of insomnia.

Of course, if you measure anything this closely with >100k participants in RCTs, it's bound to have a significant effect. But these odds ratios are not exactly small.

https://link.springer.com/article/10.1186/1617-9625-8-8

Are those numbers comparable to caffeine?

This is an apples to oranges comparison. Ideally an apples to apples comparison of the effects of nicotine and caffeine would control for method of ingestion. I wouldn't be surprised if vaping caffeine[0] has a similar odds ratio for heart attacks.

Caffeine and nicotine both exist in gum form. Have their been studies comparing that?

[0] which, to my horror, I just discovered actually exist

Thanks! Your links have convinced me

I guess vaping/nicotine, while not the worst vice out there, is still a vice lol; so they have their own dangers.

Yes, this is the correct position IMHO based on the data. This is an impossibly hard subject because so many people believe it is immoral (either from religious teaching or cultural indoctrination (like D.A.R.E., etc) and many others feel defensive like they need to justify their choices. Both of these are extremely normal human reactions, so they come by it honestly.

But vaping/nicotine can be very safe if you don't do it all the time. Occassional usage is fine. Many people naturally really like the nicotine though and have a hard time regulating their intake. If you let yourself get hooked, it can turn pretty unhealthy.

"Here is one like that: ~500k individuals, vaping has an odds ratio of 1.33 (95% CI = 1.14–1.56) for heart attacks compared to non-smoker/non-vapers."

Are vapers more likely to get a heart attack or are people with a stressful life with a higher risk of a heart attack more likely to be vapers?

Sorry. Could not resist.

This feels similar to the thing where "non-drinkers" in studies were composed of "people who had never drank alcohol" and also "recovering alcoholics".

I would imagine a chunk of vapers are people trying to transition from smoking cigarettes and still suffering from some of the ill effects.

Fair question! We would need a RCT with controls for that, perhaps one exists :)