Not that I'm proud of it, but I smoke two packs a day (trying to quit actually) and I never get sick, period. I always contributed it to either the amount of tar sitting on my lungs, or the fact I consume an above average amount of vitamin C every day for the last 10-ish years; something like 230-345mgs a day.

I suppose its also noteworthy to mention that I have never worn a mask anywhere in public, ever. I hit up the gas station every day, sometimes twice a day to get my smokes, and I shop for groceries once a week.

Also, I am acquainted with smokers that have allegedly gotten sick, but I don't know their personal smoking habits, or if they were hypochondriacs.