The Yellow Fever Board, led by then-Major Walter Reed and Jesse Lazear, had convened at the Army’s Columbia Barracks in Cuba, at the height of a deadly yellow fever epidemic ravaging Cuba in 1900.
Today, we know that yellow fever spreads when Aedes aegypti mosquitoes bite infected people, then carry the virus to the next person they bite. But in 1900, American doctors weren’t sure if the virus spread through infected blood, or through traces of infected material on bedding.
Volunteer soldiers subjected themselves to living in yellow fever survivor filth, and later to mosquito bite tests, to advance understanding of disease transmission.
This article from Kiona N. Smith at Forbes tells some of their story: The Young Soldiers Who Fought Yellow Fever And Won.
History of Vaccines
Jesse Lazear hatched Carlos Finlay’s mosquito eggs and let the mosquitoes feed on patients infected with yellow fever at a Havana hospital. The mosquitoes were then allowed to feed on study volunteers over a period of two weeks—yet no infections resulted. Two days later, however, Lazear once again allowed the mosquitoes to feed. This time, both of the men who were bitten fell ill. These experiments validated the theory Finlay had presented two decades earlier: mosquitoes (specifically, the Aedes aegypti variety) were the transmission vector of yellow fever.
AMA Journal of Ethics
Despite several prominent fatalities during the experiment’s run, Reed’s experiments were a scientific success and instrumental in establishing that yellow fever was a mosquito-borne illness. Mosquito-control initiatives based on the findings were remarkably successful and began to reduce the incidence of the violent hemorrhagic fever significantly. For years following the experiments, the honor, bravery, and heroism of the volunteers were extensively celebrated in publicity campaigns, charity drives, a government-published “Yellow Fever Roll of Honor,” popular books, a movie, and a Broadway play.
This analysis reveals that the actual self-stated motives for participation were more complex than simple honor or bravery; other factors such as ignorance of the risks, professional and occupational self-interest, and monetary inducements were pivotal.
Yale Journal of Biology and Medicine
After failed attempts at producing bacteria-based vaccines, the discovery of a viral agent causing yellow fever and its isolation in monkeys opened new avenues of research. Subsequent advances were the attenuation of the virus in mice and later in tissue culture; the creation of the seed lot system to avoid spontaneous mutations; the ability to produce the vaccine on a large scale in eggs; and the removal of dangerous contaminants. An important person in the story is Max Theiler, who was Professor of Epidemiology and Public Health at Yale from 1964-67, and whose work on virus attenuation created the modern vaccine and earned him the Nobel Prize.
The road to the current vaccine was bumpy and sometimes convoluted. The problems of attenuation of the virus in tissue culture, its large scale manufacture in eggs, and elimination of contaminants all pushed the limits of scientific knowledge of the time.