Non-snarky question: why is that a concern? Nicotine -- in the absence of burning tobacco -- isn't bad for you.
https://www.npr.org/templates/story/story.php?storyId=141164...
> AAMODT: So the changes that happen between
> 18 and 25 are a continuation of the process that starts
> around puberty, and 18 year olds are about halfway through
> that process. Their prefrontal cortex is not yet fully
> developed. That's the part of the brain that helps you to
> inhibit impulses and to plan and organize your behavior to
> reach a goal.
If nothing else, there's a monetary cost, a possible convenience cost, etc., and people should choose maturely whether that's something they want to take on.
(And there are some plausible health risks still with vaping, as others have noted.)
I'm entirely supportive of people who want to study this stuff, but the impulse that any new product should be illegal until it's been proven safe to fairly arbitrary standards seems unreasonable to me. And I think there's a bit of a baptist-bootlegger coalition between the medical researchers and tobacco companies.