Made contributions to the understanding of medicine, bacteria, and the field of public health. Particularly at U-M, Vaughan was an early proponent of the not-yet-accepted germ theory of disease. He spearheaded the campaign to open the University’s Hygienic Laboratory in 1889 — the first of its kind in the U.S. — and began his three-decade tenure as dean of the U-M Medical School in 1891. Vaughan’s experiences in the Spanish-American War and World War I spurred him to lead investigations into the nature of the 1918 flu pandemic, providing valuable data and observations.