Who developed the first effective vaccine against typhoid fever?

Almroth Edward Wright developed the first effective vaccine against typhoid fever. His killed-bacteria vaccine was developed in the 1890s and began being used to protect military personnel.

Wright worked at the Army Medical School and investigated ways to immunize people against Salmonella Typhi, the bacterium that causes typhoid fever. The vaccine used heat-killed organisms rather than live bacteria, reducing the risk of causing the disease while stimulating an immune response.

The British Army introduced typhoid vaccination for troops in the early twentieth century, and its use expanded during World War I. Typhoid vaccination helped reduce illness in military camps where sanitation and clean water were difficult to maintain.

Waldemar Haffkine also made major contributions to typhoid vaccination, especially through field work in India. That achievement is why accounts sometimes credit Haffkine with an early typhoid vaccine, but Wright is generally identified with the first effective vaccine developed for systematic military use.