Harry Plotz (April 17, 1890 - February 7, 1947) was an American Colonel in the Army Medical Corps and a noted bacteriologist. He developed a vaccine against typhoid in 1903. His research into bacterias and epidemics led to his discovery of the bacteria responsible for typhus (Rickettsia, sometimes known as Plotz's bacillus), and developed a vaccine in 1914. He was a pathologist at Mount Sinai, member of the Red Cross Commission to Serbia, and advisor to Bulgarian government on typhus fever. He spent several months in Europe investigating the spread of typhus fever in infested regions; Poland, Southern Russia and Eastern Europe. In 1942, at the Army Medical School, he found a way to restore the lost potency of typhus vaccines, sparing U.S. troops from the age-old plague of armies. He became director of the Virus and Rickettsial division of the Medical Corps Reserve, but died suddenly in 1947.