I had 2 Pfizer shots and then 4 months later I had Covid-19.
That's probably what's known as a breakthrough infection. You know all those stories about Pfizer and Moderna being over 90% effective? As it turns out, 90% is not 100%...
My 3 sons had breakthrough too. My wife was the last to get it had no shots.

For a oversimplified version of what I’m trying to use with my question. What would be the independent and dependent variables for spread of Covid (carriers). And the conditional variables as well, like secondary requirements that must be met to add to the number of Covid being spread.