There was a study recently showing that vaping negatively affects protective cells in lung tissue which may result in lung inflammation[1]. Their results were not related to flavours -- they specifically used flavourless fluid, instead they were concerned with vegetable glycerin and propylene glycol (the primary components of e-cigatette fluid).

Obviously vaping is preferable to smoking, but I have serious doubts that inhaling air isn't preferable to vaping.

[1]: https://thorax.bmj.com/content/73/12/1161