medrxiv.org/content/10.110…

That's a "trivial" fact that was overseen by our top virologist, but is now discussed by main stream epidemologist
1. Biological - we have innate immunity, that works for one individual better than another. On diamond princess, only 1/4 got infected.
en.m.wikipedia.org/wiki/Red_Queen…
2. Behivorial - Robinson Crusoe has another susceptibility than NYC metro user.
