The South African-born American epidemiologist and microbiologist Max Theiler (1899-1972) received the 1951 Nobel Prize in physiology or medicine for developing a vaccine for yellow fever.

Max Theiler was born in Pretoria, South Africa, on January 30, 1899. His early schooling was in Pretoria and, because his father was Swiss, in Basel. Partly influenced by his father, who was a veterinary scientist, Max decided on a career in medicine, and in preparation he attended Rhodes University College in Grahamstown, South Africa, and the University of Capetown.

In 1911 Theiler enrolled at St. Thomas's Hospital, a well-known teaching hospital in London. In 1922 he was licensed to practice by London's Royal College of Physicians. The idea of medical practice, however, no longer appealed to him, and he enrolled in the London School of Tropical Medicine and Hygiene. Later that year he went to the United States, as he had been offered a position in the Department of Tropical Medicine at Harvard Medical School. While at Harvard he studied amebic dysentery and rat-bite fever, but his most far-reaching work was on yellow fever.

When Theiler began work on yellow fever, it was already known that a virus was responsible for the disease, that it was commonly transmitted by a mosquito, and that the disease could be controlled in populated areas by eradication of the breeding grounds of the mosquitoes. Still, an effective method of inoculation was necessary for full protection. One of Theiler's earliest contributions to the development of a yellow fever vaccine was the demonstration that laboratory white mice could be infected with the virus. When he introduced the yellow fever virus from a monkey into the brain of a white mouse and successively transferred the virus through several mice, he found that the virus underwent certain changes. It became progressively more serious in its effects on the mice, but at the same time its effects on monkeys lessened. These findings were the foundation of a mouse-derived vaccine.

In 1928 Theiler married Lillian Graham. Two years later he joined the Rockefeller Foundation in New York City to continue his work on yellow fever. The mouse-derived vaccine was being used cautiously on humans by some researchers, but Theiler felt it was not safe enough for general use. Within a few years he succeeded in developing a vaccine called 17D, derived from a chick embryo, which proved both safe and effective and is now widely used in human immunization against yellow fever. His discovery was announced in 1937 in the Journal of Experimental Medicine. After that his work was concerned with other insect-borne virus infections.

In 1950 Theiler became director of the virus laboratories of the Rockefeller Foundation and the following year director of the division of medicine and public health. In 1964 he was appointed professor of epidemiology and microbiology at Yale University.

Theiler retired from Yale in 1967. Although he immigrated to the United States in 1923, and remained there until his death on August 11, 1972 at the age of 72, he never applied for U.S. citizenship.

Further Reading on Max Theiler

Theodore L. Sourkes, Nobel Prize Winners in Medicine and Physiology, 1902-1965 (1953; rev. ed. 1967), was a good introduction to Theiler and his work. See also Nobel Foundation, Physiology or Medicine: Nobel Lectures, Including Presentation Speeches and Laureates' Biographies, vol. 3 (1967). Some added insight was gained from Greer Williams, Virus Hunters (1959), and a detailed study of the entire yellow fever problem was in H. Harold Scott, A History of Tropical Medicine (2 vols., 1939).