I imagine there is no definitive answer due to lack of information as to the full ingredients of the liquid as general knowledge( i don’t now whats in them, or how or if the additives are controlled/regulated/tested etc.)

One of the issues with traditional cigarettes (this is aside from the obvious inhaling red hot smoke into lung tissue) are the chemicals added by the manufacturer to aid in the delivery of the nicotine as fast as possible to the receptors in the brain, which is the main cause of the intense ‘hit’ and the subsequent difficulty in stopping smoking.

I suspect they are less damaging than fags, but if the same cocktail of additives are used, maybe not much so.