text: The development of drugs for the treatment of infectious diseases was a major focus of early research and development efforts; in 1900, pneumonia, tuberculosis, and diarrhea were the three leading causes of death in the United States and mortality in the first year of life exceeded 10%.
  In 1911 arsphenamine, the first synthetic anti-infective drug, was developed by Paul Ehrlich and chemist Alfred Bertheim of the Institute of Experimental Therapy in Berlin. The drug was given the commercial name Salvarsan.  Ehrlich, noting both the general toxicity of arsenic and the selective absorption of certain dyes by bacteria, hypothesized that an arsenic-containing dye with similar selective absorption properties could be used to treat bacterial infections.  Arsphenamine was prepared as part of a campaign to synthesize a series of such compounds, and was found to exhibit partially selective toxicity. Arsphenamine proved to be the first effective treatment for syphilis, a disease untl then had been incurable and led inexorably to severe skin ulceration, neurological damage, and death.
  Ehrlich's approach of systematically varying the chemical structure of synthetic compounds and measuring the effects of these changes on biological activity was pursued broadly by industrial scientists, including Bayer scientists Josef Klarer, Fritz Mietzsch, and Gerhard Domagk. This work, also based on the testing of compounds available from the German dye industry, led to the development of Prontosil, the first representative of the sulfonamide class of antibiotics.  Compared to arsphenamine, the sulfonamides had a broader spectrum of activity and were far less toxic, rendering them useful for infections caused by pathogens such as streptococci.  In 1939, Domagk received the Nobel Prize in Medicine for this discovery. Nonetheless, the dramatic decrease in deaths from infectious diseases that occurred prior to World War II was primarily the result of improved public health measures such as clean water and less crowded housing, and the impact of anti-infective drugs and vaccines was significant mainly after World War II.
  In 1928, Alexander Fleming discovered the antibacterial effects of penicillin, but its exploitation for the treatment of human disease awaited the development of methods for its large scale production and purification.  These were developed by a U.S. and British government-led consortium of pharmaceutical companies during the world war.
  There was early progress toward the development of vaccines throughout this period, primarily in the form of academic and government-funded basic research directed toward the identification of the pathogens responsible for common communicable diseases. In 1885, Louis Pasteur and Pierre Paul Émile Roux created the first rabies vaccine. The first diphtheria vaccines were produced in 1914 from a mixture of diphtheria toxin and antitoxin (produced from the serum of an inoculated animal), but the safety of the inoculation was marginal and it was not widely used. The United States recorded 206,000 cases of diphtheria in 1921, resulting in 15,520 deaths.  In 1923, parallel efforts by Gaston Ramon at the Pasteur Institute and Alexander Glenny at the Wellcome Research Laboratories (later part of GlaxoSmithKline) led to the discovery that a safer vaccine could be produced by treating diphtheria toxin with formaldehyde. In 1944, Maurice Hilleman of Squibb Pharmaceuticals developed the first vaccine against Japanese Encephalitis. Hilleman later moved to Merck, where he played a key role in the development of vaccines against measles, mumps, chickenpox, rubella, hepatitis A, hepatitis B, and meningitis.