Similar mechanisms may be at play in boosting the efficacy of the vaccine. At least, I thought I once saw a suggestion that physical activity might be beneficial concurrent with getting vaccinated - it supposedly improves the immune response. I don't know if that was ever studied, but like a good, obsessive health nut I made the most of it. When the pandemic started I amped up my running in spite of the dirty looks I got from all the locked-down, germaphobic walkers who were suddenly crowding my routes. (And even the most sane of us had turned into a germaphobe!) And in the days surrounding my vax and booster I dragged myself out to run as though I was swallowing medicine. And look -- I've yet to suffer any Covid symptoms, even though I've shared a house with those who have. Yeah, I realize that this is anecdotal. Just saying.

And of course, this could be only correlation without causation. That is, having an effective immune response might be the primary reason anyone is able to remain (and report being) "always active" as well as why they're so much less likely to die. A person's activity level could be nothing but an inconsequential feature.