Good points zoiDman. Even if you had virgin vapers to test on though, I don't think the particular kind of trialing you're alluding to would produce any definate scientific results, since there are infinate variables on testing individual in an uncontrolled environment that can't be controlled. I think you would have to be testing in a controlled lab environment on a cellular level. In this way you could use 'virgin' culture and expose it to variable environments and compare data etc. This is not ideal either, since you can't test on the human as a whole, and you can't take into account what may happen on a time scale, with the body's ability to heal itself and cope with certain exposures as a whole organism. But this remains a problem for medical research in general and we can only work with what we have. I don't really see how scientifically testing the effects of vaping would be more difficult than testing the effects of any other environmental exposure on/in the body.
I think your starting to understand just how Difficult obtaining Meaningful results are from a clinical trial. Any Clinical Trial. No matter who the Funder is or perhaps for a Desired Result.
The Best way is to just "Fudge" the data until you get the Results You Want.
It's a Time Honored Technique.