Vaporizers, E-Cigs, hookah pens, etc. are all terms used to describe what the FDA calls Electronic Nicotine Delivery Systems (ENDS). The organic compounds along with the vaporized water contain nicotine and other compositions of flavors. In 2016, the FDA extended their ruling and passed regulation to cover all tobacco products and ENDS devices that meet the definition of a tobacco product. In most cases, the only substance in common with e-cigarettes and normal cigarettes is nicotine. The amount of nicotine can also differ in both. For this reason, I think e-cigs can be considered different from normal cigarettes in terms of regulation. Normal cigarettes contain many more substances that are significantly more harmful than that of the contents in e-cigs. As a result, regulating normal cigarettes is not as easy of a decision to make. Because of the additional harmful chemicals in normal cigarettes along with tobacco, it is harder for the FDA to regulate. On the contrast, an e-cig can be considered a medical device and has very few chemicals making it drastically different. E-cigs can be used by people who are fighting addiction to normal cigarettes as well. I believe a lot more can be done with e-cigs if they are put through a full clinical trial.

reference: https://www.fda.gov/TobaccoProducts/Labeling/ProductsIngredientsComponents/ucm482563.htm#regs