Proof of the therapeutic action in vivo of penicillin against streptococcal and other bacterial infections. Building upon Fleming’s work (No. 1933 and 10784), the consequences of which had originally been widely unappreciated, even by Fleming himself, Chain and his co-workers concentrated penicillin and showed that it was probably the most effective chemotherapeutic drug known, and that it was relatively non-toxic. This led to mass production of the drug, which has saved untold millions of lives. Biography of Florey by G. Macfarlane, 1979.

In 1945 Chain and Florey shared the Nobel Prize in Physiology or Medicine with Fleming "for the discovery of penicillin and its curative effect in various infectious diseases."