Maybe helping create the non shot database? No shot button selected, use credit card to pay, now the no shot status is linked to that credit card account, ie, you. Govt collects credit card records instantly gets a list of people with addresses of where the non compliant live??

As far as I am aware there isn't any type of national database that exists tracking this shot status. Most of those who took it proudly proclaim how they've done such. These people don't care if you already got the shot because they just keep making you take more. It's those pure blood folks that they are really concerned about.

Pure speculation but plausible imo.