Alexander Fleming won the Nobel Prize in Physiology or Medicine in 1945. He shared the award with Howard Florey and Ernst Chain for the discovery of penicillin and its curative effect in infectious diseases.
Fleming first observed penicillin’s antibacterial action in 1928, but the discovery did not immediately become a usable treatment. Florey, Chain and their colleagues at Oxford developed ways to cultivate the mold, extract the active compound and test it safely. Their work helped turn Fleming’s laboratory observation into a practical medicine.
The Nobel Assembly announced the award on 25 October 1945, after penicillin had demonstrated its value during the Second World War. Mass production helped treat bacterial infections in wounded soldiers and contributed to the antibiotic’s rapid adoption after the war.
A common misunderstanding is that Fleming alone developed the finished drug. The 1945 prize recognized a collaborative achievement: Fleming discovered the antibacterial substance, while Florey, Chain and their teams advanced its purification, testing and medical use. The three men divided the prize equally.