Almost 15 years after Penicillin discovered, most of the world's serious penicillin cases had been treated by one doctor : Martin Henry Dawson

1943 Annual Report, Columbia University

In the Spring of 1943, Columbia University released its Annual Report and mentions , in passing, that Dr MH Dawson had supervised the treatment of 65 serious cases with penicillin for the National Research Council.

(Generally Columbia's lengthy wartime annual reports successfully managed to avoid talking about penicillin - a sure sign that it was ignored by academic science elsewhere as well throughout the war.)

If we can take "serious" to mean "treated systemically" , that probably means that the largest percentage of the world's systemic penicillin cases up to that point in time had been done by Dr Dawson alone !