Dr. Richard G. Henderson, wearing his Public Health Service uniform, holds his infant son William while his daughter Sue cradles her doll, about a year before he would die of typhoid fever. During World War II, scientists at NIH developed vaccines for diseases likely to infect our troops overseas. Henderson worked on standardizing typhus vaccine, demonstrating the existence of a toxin produced by epidemic typhus in egg yolk sac cultures (which were used for vaccine development) which enabled the researchers to develop a mouse neutralization test. Henderson and his laboratory aide Leroy Snellbaker both became ill with typhus. Henderson died on October 20, 1944.