Richard Friedrich Johannes Pfeiffer FRS (27 March 1858 – 15 September 1945) was a German physician and bacteriologist. Pfeiffer was born to Otto Pfeiffer, a German pastor of the local Evangelical parish, and Natalia née Jüttner, in Treustädt, Province of Posen (Prussia), and died in Bad Landeck (Prussia, now Poland). Career Pfeiffer is remembered for his many fundamental discoveries in immunology and bacteriology, particularly for the phenomenon of bacteriolysis. In 1894 he found that live cholera bacteria could be injected without ill effects into guinea pigs previously immunised against cholera, and that blood plasma from these animals added to live cholera bacteria caused them to become motionless and to lyse. This could be inhibited by previously heating the blood plasma. He called this bacteriolysis and it became known as the Pfeiffer Phenomenon, or Isayev-Pfeiffer phenomenon. Working with Robert Koch in Berlin he intellectually and experimentally conceived the concept of endotoxin as a heat-unstable bacterial poison responsible for the pathophysiological consequences of certain infectious diseases. Endotoxin and anti-endotoxin antibodies have since then fascinated researchers of many disciplines, particularly in the fields of diagnosis, prevention, and therapy of severe Gram-negative infections. Pfeiffer was a pioneer in typhoid vaccination. He discovered the specific bacteria-dissolving immune bodies in cholera and typhus. The British pathologist Almroth Wright is generally credited with the initiation of typhoid vaccination in 1896. His claims of priority were challenged as early as 1907 in favour of Richard Pfeiffer. A review of the original literature of the 1890s and the early 1900s revealed that several groups were working on typhoid vaccine at the same time and that the credit for the initiation of typhoid vaccine studies should be shared by these two great researchers. In 1892, Pfeiffer isolated what he thought was the causative agent of influenza. The culprit, according to Pfeiffer, was a small rod-shaped bacterium that he isolated from the noses of flu-infected patients. He dubbed it Bacillus influenzae (or Pfeiffer's bacillus), which was later called Haemophilus influenzae. Few doubted the validity of this discovery, in large part because bacteria had been shown to cause other human diseases, including anthrax, cholera, and plague. When the Spanish flu, the history's deadliest known influenza pandemic, began in 1918, most scientists believed that Pfeiffer's bacillus caused influenza. With the lethality of this outbreak (which killed an estimated 20 to 100 million worldwide) came urgency—researchers around the world began to search for Pfeiffer's