In 1915 the International Health Division (IHD) made the research and eradication of yellow fever and malaria its top priorities. While the organization achieved success in both campaigns, its yellow fever initiative yielded the clearest positive results. Before World War II, the IHD expended half of its budget on yellow fever programs, which culminated in the development of a successful yellow fever vaccine. This funding also contributed to the building of a wide and effective network of research laboratories, as well as the development of important scientific careers through support for individual fellowships.
Mosquito transmission as the cause of yellow fever was first proposed by Carlos Finlay in 1881 and proven by Major Walter Reed of the US Army in 1900. This discovery led General William C. Gorgas to implement anti-mosquito measures while supervising the building of the Panama Canal; earlier attempts at construction had failed partly because of the prevalence of yellow fever among workers. Once the canal was completed, many public health experts feared that increased international travel and shipping would lead to a sudden expansion of the disease.
Concern about the spread of yellow fever prompted Rockefeller Foundation (RF) interest in eradicating yellow fever. After Gorgas’ success in mosquito control in Panama, the RF recruited him in 1916 to chair the newly formed Yellow Fever Commission and to direct its efforts in eradication. Gorgas focused on vector control. He aimed to destroy mosquito breeding grounds in key communities, or “seedbeds,” where the aedes aegypti mosquitoes lived alongside a non-immune population. The first successful IHD campaign in yellow fever eradication took place in Guayaquil, Ecuador.
More ambitious projects were to follow. One of the most significant campaigns began in 1923 when the Brazilian Government requested IHD assistance in its efforts to eradicate yellow fever. For the next 17 years the IHD took the lead role in this campaign and even after the Brazilian Government took charge of the program in 1940, the IHD remained involved, contributing major support towards the cost of field work and lab tests.
Although its early work in yellow fever was concentrated in South America, the IHD began to redirect a large portion of its funding to Africa in 1929. In that year the agency established its first African research laboratory in Lagos, Nigeria, and created the West Africa Yellow Fever Commission.
Creating a Vaccine
As with other IHD initiatives, efforts to combat yellow fever in the field complemented efforts in the laboratory to develop new cures for the disease. In 1925, a promising yellow fever vaccine was being tested in the labs of the Rockefeller Institute in New York. The vaccine was developed by Hideyo Noguchi, a respected Rockefeller scientist who had earlier made advancements in the study of syphilis and Oroya fever. In this case, however, Noguchi had erred. In 1927 IHD scientists in Africa discovered that Noguchi’s findings were related not to yellow fever, but to a bacterial infection called Weil’s disease. Noguchi sailed for Africa to undertake further research, but seven months later he contracted yellow fever and died from the disease.
His death was mourned by the medical community, who viewed him as a “martyr to science.” Noguchi was one of six RF researchers who died while studying yellow fever, a statistic that almost caused IHD Director Frederick F. Russell to abandon the campaign against the disease.
In spite of the fatalities, and the disappointing results of Noguchi’s work, the search for a vaccine remained a top priority. The ultimate discovery of the vaccine, 17D, remains a high-point in RF medical research.
Max Theiler, who came to the IHD in 1930, worked intensively on the development of a yellow fever vaccine in the IHD’s New York laboratories and by 1936, he and his associates had developed an effective vaccine. The IHD funded the first field trials of the vaccine in Brazil in 1937, and following the success of these trials, the RF funded large-scale manufacturing of the vaccine. Theiler’s 17D vaccine remains the primary vaccine against yellow fever, and Theiler would go on to win the Nobel Prize in 1951 for his work
During World War II, the RF was asked to coordinate the vaccination of American and British military personnel. However, in 1942, outbreaks of jaundice were reported among some military personnel who had been vaccinated with 17D. In total 8 million doses of vaccine had been administered to soldiers, 80,000 of whom developed jaundice, resulting in 81 deaths. Further research revealed that the cases occurred in soldiers injected with particular batches of the vaccine that had been tainted by infected human blood. Vaccinations were halted until a new vaccine containing no human serum could be produced. 
Passing the Torch
Following the war, and the administration of 34,000,000 vaccines (funded by the RF), the manufacture and distribution of the yellow fever vaccine passed from the RF to the United States Public Health Service, as well as other international institutions and government agencies. While the IHD continued working on yellow fever, largely focusing on prevention rather than cure, the importance of yellow fever research waned.
The success of the yellow fever research and vaccination campaign had an immense impact on the reputation and direction of the IHD. Disease identification and the development of vaccines solidified the IHD record of producing high quality research, and the discovery of the yellow fever vaccine appeared to validate the IHD’s decision to shift its priorities from the development of public health institutions toward the funding of scientific research.