Not to imply you suggested otherwise, but smoking costs far more life years than the coronavirus. Anyone quitting is doing a good thing for the wrong reason.
Vaping is less clear--I do think there's some non-negligible chance that for the next couple years, it will be a net benefit to public health. That would be funny, considering how hard the public health authorities worked to smear nicotine vaping with the deaths from adulterated (vitamin E acetate) marijuana cartridges last summer.
I think it's too early to absolutely determine the life expectancy cost of a covid infection. The pathology is so diverse with this virus it would take a very complex calculation and obviously years of observation to make your claim.
To quote this paper's author: "This virus is unusual and it's hard not to take a step back and not be impressed by how many manifestations it has on the human body"
and to quote the paper itself: "In a study of nearly 5,500 patients admitted with COVID-19 in a New York City hospital system, (acute kidney injury) occurred in 37%, with 14% of the patients requiring dialysis. "
and that is only one of dozens of conditions in their findings.
Patients who die of coronavirus have median age of 78[1], and thus life expectancy around ten years. Younger decedents will have a disproportionate effect on average life years lost, so using the median life expectancy does tend to underestimate that. On the other hand, the patients who die were probably less healthy than the average for their age before they got infected (e.g., the huge mortality in nursing homes; nursing home patients already had an average life expectancy around a year[3]), which would make us overestimate. Somewhat arbitrarily, let's say those cancel, so a coronavirus death costs ten years of life.
The average IFR over all ages is 0.7%[4] from a recent meta-analysis. If we're considering prospective smokers, then I guess we should exclude young children, so let's (again, somewhat arbitrarily) bump that up to 1%. That would mean a coronavirus infection in a random individual (age weighted according to population of prospective smokers) costs 0.1 years of life expectancy.
But smokers have life expectancy about ten years[5] shorter than non-smokers! So there's lots you could find to argue about in my rough calculation above, and I agree that patients who don't die immediately still lose some yet-unknown number of quality-adjusted years of life; but unless you think you can find two orders of magnitude, smoking is unquestionably more dangerous. That doesn't mean the coronavirus is harmless, just that smoking is really bad.
You may not know and it may be very hard to determine the ultimate loss of life expectancy in younger people. I read somewhere that people that survived a bad bout of polio often suffered poor health later in life. Long term kidney damage could easily be something a person could live with for decades before it came back to bite them.
Using the adulterated marijuana cartridges as a way to push anti-vaping campaigns was the same sort of disingenuous technique use to get people to not wear masks to save them for health care professionals at the beginning of the COVID epidemic. The authorities think the public are too stupid to understand or react to facts, so they lie to them and it ends up backfiring.
Uhm. It ended up backfiring in the US. Here in the Netherlands they said the same thing about masks (and made it pretty clear why this was said) and it ended up being just fine. It seems abundantly clear that your authorities simply had no such plan in mind.
I mean because nicotine might be protective against the coronavirus, and that protective effect might outweigh the harm of vaping. Certainly not proven (and please nobody start vaping because of that), but there's some weak evidence and it's funny.
Of course vaping's real benefit to public health comes from smoking cessation as you say, since smoking is (per my comment above) really deadly. I was disturbed to see the public health authorities blaming nicotine vaping for the lung injuries last summer, given (a) the ample evidence for vitamin E acetate as the cause; and (b) the cost in mortality from smokers who got scared by their misleading warnings and either didn't switch to vaping or switched back to cigarettes.
Vaping is less clear--I do think there's some non-negligible chance that for the next couple years, it will be a net benefit to public health. That would be funny, considering how hard the public health authorities worked to smear nicotine vaping with the deaths from adulterated (vitamin E acetate) marijuana cartridges last summer.