South African medical researcher Max Theiler develops the yellow fever vaccine at the Rockefeller Foundation in New York City.

South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. Its nine provinces are bounded to the south by 2,798 kilometres of coastline that stretches along the South Atlantic and Indian Ocean; to the north by the neighbouring countries of Namibia, Botswana, and Zimbabwe; to the east and northeast by Mozambique and Eswatini; and it encloses Lesotho. Covering an area of 1,221,037 square kilometres, the country has a population of over 63 million people. Pretoria is the administrative capital, while Cape Town, as the seat of Parliament, is the legislative capital, and Bloemfontein is regarded as the judicial capital. The largest, most populous city is Johannesburg, followed by Cape Town and Durban.

Max Theiler was a South African-American virologist and physician. He was awarded the Nobel Prize in Physiology or Medicine in 1951 for developing a vaccine against yellow fever in 1937, becoming the first African-born Nobel laureate.

Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains—particularly in the back—and headaches. Symptoms typically improve within five days. In about 15% of people, within a day of improving the fever comes back, abdominal pain occurs, and liver damage begins causing yellow skin. If this occurs, the risk of bleeding and kidney problems is increased.

A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates the immune system to recognize the agent as a threat, destroy it, and recognize further and destroy any of the microorganisms associated with that agent that it may encounter in the future.