The only Nobel Prize ever awarded for inventing a vaccine

Max Theiler spent years passing yellow fever virus through mice and chicken embryos, weakening it strain by strain until it triggered immunity without causing disease. His 17D vaccine, released in 1937, is still used worldwide today. In 1951 it earned him the Nobel Prize in Physiology or Medicine, the only Nobel ever awarded for developing a vaccine.

— Max Theiler, Max Theiler — Nobel Prize in Physiology or Medicine, 1951