The science isn’t fully decided on vapes - AFAIK the PG/VG and nicotine are relatively harmless (though nicotine does carry some heart/stroke risks) but the flavours are generally only tested for safety when taken orally, not when atomised and inhaled. Flavourless vape juice is therefore probably safe, though hardly anybody sells it, it’s kinda unpleasant, and it does still carry some health risks.