On Sept. 30, 1911, typhoid immunization became required of all U.S. service members. The U.S. Army became the first military organization in the world to make typhoid vaccination mandatory, and had the lowest typhoid fever incidence of any major combatant in World War I.

The first typhoid vaccines were created in Britain in 1896 by Almroth Wright, and in 1897 Sir Willian B. Leishman of the Royal Army Medical Corp., created a more potent and less toxic version. Captain Frederic Russell of the U.S. Army subsequently modified Leishman’s vaccine to create a subcutaneous form and conducted volunteer studies demonstrating safety and efficacy.