Smoking reduces 14 years of life, on average.
However, vaping is not in the same equation here. It is an alternative to smoking.
According to the National Academies of Science:
“Laboratory tests of e-cigarette ingredients, in vitro toxicological tests, and short-term human studies suggest that e-cigarettes are likely to be far less harmful than combustible tobacco cigarettes.”
People think that nicotine causes cancer. Nicotine is addictive, but it’s the other chemicals in the smoke that kills. Without the cancerogenic cocktail in tobacco smoke, nicotine is not much different than caffeine.
Yes, there can be some other contaminants in vapor, but for nationally known brands (eg, Juul), they are subject to regulation and litigation and must be very careful. And even for lesser known manufacturers, the existing research indicates that they are far less toxic than cigarettes.