Seems to me there are a lot of factors that could influence this. For example, maybe the non-jabbed, those freedom loving, government distrusting vermin, travel more, because they don't buy into the "stay at home and be a mouse in a cell" narrative. Just as one example.

Couldn't be bothered (!) to really do a serious analysis of the study, but on the surface, it looks exactly like a project set up not to examine objectively, but to build a narrative towards a for-gone conclusion. Aka propaganda.