Most of the nicotine used in vapes is very cheap Chinese nicotine.Peers and advertising.
Medical grade perhaps, properly administered.
Unless a company specifically says they are using quality made S-nicotine(synthetic) it is probably very low quality, high impurity Chinese made S-nicotine, which has been found to have a lot of undesirable chemicals.
The "good" stuff is used in nicotine gums and patches, as well as some treatments for Alzheimer's and other forms of dementia.....and "good" vape juice made NOT in China.
BUT, some studies have found that even nicotine from smoking tobacco can have positive effects on cognition, anxiety and depression. As well it can be a mild hunger suppressant for some eating disorders.
The point is, nicotine, in the amount used, is not the most dangerous chemical in poorly made vape juice. Some of the chemicals used for nicotine delivery in bad vape juice are FAR more dangerous than the nicotine.
A decade ago a friend of mine opened a vape shop when vaping was just getting popular. He did a LOT of research and still does, pure S-nicotine is no joke. One mistake in handling or mixing and you could be dead. Most hospitals do not have the resources for a massive nicotine overdose. There are more hospitals ready for it now than 10 years ago,but most still don't know what to do. You do not have long, and may not make it out of the vape shop....its that deadly.
A decade ago when my friend started his shop, it was like the wild west. A bunch of novices trying to master mixing dangerous chemicals with absolutely zero training and no oversight.