Max Theiler developed the 17D yellow fever vaccine and received the 1951 Nobel Prize in Physiology or Medicine.
Working at the Rockefeller Foundation, Theiler weakened the yellow fever virus through repeated passage in mouse tissue and chicken embryos. This produced the 17D strain, which could stimulate protection without causing ordinary yellow fever in vaccinated people. The vaccine became one of the most important tools against a mosquito-borne disease.
Theiler’s work built on earlier research showing that yellow fever was caused by a filterable virus and transmitted by mosquitoes. The 17D vaccine has been used internationally for decades, especially for people living in or traveling to areas where yellow fever circulates.
Yellow fever vaccination is not the same as treatment after infection: the vaccine is preventive, while severe cases require supportive medical care. Theiler was the first Nobel laureate recognized for developing a virus vaccine.