That is an excellent article linked by Lydia above, and there are many like it. Core tobacco control industry members such as Prof Britton have said things like,"If all smokers switched to ecigs then 5 million lives would be saved just among those alive today in the UK" (paraphrased). If 5 million lives can be potentially saved in a small place like the UK then you can multiple that by 4 or 5 to get the US equivalent.
There are many such statements by the acknowledged experts. Another is: "Three months of additional smoking poses a greater risk to someone’s health, on average, than a lifetime of using a low-risk alternative."
- CV Phillips
In contrast, people who aren't experts in THR or who are paid by commercial rivals, say things like, "We just don't know".
On balance, you should be aware of two facts:
1. Vaping is a lot safer than smoking - on average. If you guessed at 100 times safer then that would probably be on the low side. We won't know the full story for 20 years, but at present it's hard to find any disease route that will kill thousands of people. A handful will certainly die but this is inevitable with any type of activity at all, and will most likely be way below any statistically identifiable quantity.
2. There is no such thing as 'vaping' in terms of one activity that can be monitored and measured. There is a wide variety of usage modes, product types and refill types.
a. Vaping 2ml a day does not entail the same risk elevation as vaping 10ml a day.
b. Using an eGo running at 7 watts does not entail the same risk elevation as use of an RBA running at 40 watts.
c. Consuming small quantities of ecopure does not entail the same risk elevation as consumption of large quantities of unicorn milk or butter custard cream.
Daily vaping of 2ml of ecopure out of a standard eGo is not the same as vaping 10ml a day of creamy custard out of a sub-ohm RBA. There is likely to be a considerable risk elevation in the second case compared to the first. While it is not inconceivable that the first case involves a risk reduction compared to smoking of around 10,000 times, the second case might only involve a risk reduction of 10 times. We won't know for 20 years as these are long-term issues. We'll have an excellent idea in about 10 years time (as by then we'll have 18 years of info), but it will take 20 years to get the stats.
There is no such thing as 'vaping' if you are talking about measuring risks and health impact - there are just too many variables.
You pays your money and takes your choice
- so choose according to your priorities.