Developed by the G.H. Sherman Bacteriological Laboratories, Detroit, Sherman’s Influenza Vaccine No. 38 represents an early attempt to prevent influenza following the devastating 1918 Spanish flu pandemic. The vaccine contained a combination of bacterial strains, including influenza bacillus, pneumococcus, streptococcus, staphylococcus, and Micrococcus catarrhalis, reflecting the prevailing belief that bacteria were responsible for influenza. At the time, the true cause of influenza remained uncertain. The human influenza virus was not isolated until 1933, making this 1937 vaccine an important historical example of how scientific understanding evolved from bacterial theories toward modern viral vaccines. The specimen offers a fascinating glimpse into the early history of influenza prevention and vaccine development.