There are large crowds that took 2 doses in pandemic period (getting vaccinated properly back at the time) but not receiving boosters.

It would be easy to track:

- 2 dose, no other booster

- all boosters

- no vaccine

and readjust results considering age and other bias etc.

If all booster people have excess deaths, than "not from Covid" ? If 2 dose people excess deaths < all boosted people, than something about vaccine? No vaccine could be control.