The J&J/Janssen vaccine requires only one dose as well, and you can get the green certificate after the single dose. Since the format encodes 'doses received' a

The J&J/Janssen vaccine requires only one dose as well, and you can get the green certificate after the single dose. Since the format encodes 'doses received' and 'total number of doses' separately, I would guess that people with prior illness can similarly get the total dose number set to 1 there.