> I do think that it suggests that the current CDC guidance (of recommending 2 doses even for those previously infected) might be overkill and that it would be worth further study of whether 1 dose (or even 0 doses) would be sufficient (including against variants) for those previously infected.

We agree on this.

> I don't know of any study of the Delta variant (or other recent variants) comparing immunity acquired from infection versus immunity conferred by vaccination -- AFAIK, it's still unknown how these compare and whether a vaccination might provide additional immunity against variants.

I'm not aware of any study of this, either. So far, everyone is focusing on the vaccines.