(1899-1972) South African–born US microbiologist who developed an effective vaccine against yellow fever, which gained him the 1951 Nobel Prize for Physiology or Medicine. He also researched into various other diseases, including Weil's disease and poliomyelitis.
Theiler was born in Pretoria and began his studies in South Africa, completing them in the UK at St Thomas's Hospital and the London School of Hygiene and Tropical Medicine. In 1922 he immigrated to the US. From 1930 to 1964 he worked at the Rockefeller Institute for Medical Research (now Rockefeller University), New York City, becoming director of the Virus Laboratory there in 1950. He ended his career as professor at Yale.
Theiler used albino mice in his work on yellow fever, and eventually combined the mouse-adapted viral strain with serum from the blood of people who had recovered from yellow fever and injected the mixture into humans. This produced immunity without affecting the kidneys, and was the first safe vaccine against yellow fever.
However, human serum containing antibodies against yellow fever is difficult to obtain. Theiler therefore began culturing the virus in chick embryos, and in 1937 he developed vaccine 17-D, still the main form of protection against yellow fever.