A "positive" result was represented by clumping of bacteria, indicating that the body was producing anti-serum (now called antibodies) against the pathogen.Citing the example of the Second Boer War, during which many soldiers died from easily preventable diseases, Wright convinced the British Army that 10 million vaccine doses should be produced for the troops being sent to the Western Front, thereby saving up to half a million lives during World War I. The British Army was the only combatant at the outbreak of the war to have its troops fully immunized against the bacterium. For the first time, their casualties due to combat exceeded those from disease.In 1909, Frederick F. Russell, a U.S. Army physician, adopted Wrights typhoid vaccine for use with the Army, and two years later, his vaccination program became the first in which an entire army was immunized. It eliminated typhoid as a significant cause of morbidity and mortality in the U.S. military. Typhoid vaccination for members of the American military became mandatory in 1911. Before the vaccine, the rate of typhoid fever in the military was 14,000 or greater per 100,000 soldiers.
As of 2018, chronic typhoid carriers must sign a "Carrier Agreement" and are required to test for typhoid shedding twice yearly, ideally every 6 months. Carriers may be released from their agreements upon fulfilling "release" requirements, based on completion of a personalized treatment plan designed with medical professionals. Fecal or gallbladder carrier release requirements: 6 consecutive negative feces and urine specimens submitted at 1-month or greater intervals beginning at least 7 days after completion of therapy. Urinary or kidney carrier release requirements: 6 consecutive negative urine specimens submitted at 1-month or greater intervals beginning at least 7 days after completion of therapy. As of 2016 the male:female ratio of carriers in Los Angeles county was 3:1.Due to the nature of asymptomatic cases, many questions remain about how individuals are able to tolerate infection for long periods of time, how to identify such cases, and efficient options for treatment. Researchers are currently working to understand asymptomatic infection with Salmonella species by studying infections in laboratory animals, which will ultimately lead to improved prevention and treatment options for typhoid carriers. In 2002, Dr. John Gunn described the ability of Salmonella sp. to form biofilms on gallstones in mice, providing a model for studying carriage in the gallbladder.