<prompt> Which events occurred before 1900 ADEstablishment of seat of social medicine at OxfordUse of BCG vaccineEpidemiological work on cholera by John SnowWork on scurvy by james Lind  <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. 