I use Z23 as the diagnosis code, and use CPT codes 0001A and 0002A for Pfizer first and second doses, and 0011A and 0012A for Moderna first and second doses. I filed both the first and second doses on the same claim. The last claims I filed paid a total of 28.39, which is an average of the first and second dose fees as approved by Medicare. This was before we were notified that Medicare will pay up to $40 per shot. Hope this helps!