NCTR research or any scientific research is not going to come out super fast.
https://www.fda.gov/AboutFDA/CentersOffices/OfficeofMedicalP...
disclaimer: my view is my personal view and not that of FDA.
(One of the first things Canada did when making marijuana legal was to make "no smoking" zones extend to marijuana, too.)
The only concern with vapes like the juul is that while their base components are safe to vape, sometimes they use flavors which are not very well studied (and which, when heated, may degrade into carcinogenic chemicals).
It's because of the obnoxious metonymy "nicotine -> cigarette smoke" that appears even in research paper titles.
Personally I believe (and afaik current science supports that) vaping to be far safer, but it's probably not safe and there are a lot of unknowns left.