<prompt> Which events occured before 1900 ADEstablishment of seat of social medicine at OxfordWork on scurvy by james LindEpidemiological work on cholera by John SnowUse of BCG vaccine  <response>: An english epidemiologist John Snow studied the epidemiology of cholera in London from 1848-1854 and established the role of polluted drinking water in spread of cholera. 