Question: When did blood transfusions become safer and why?
Answer: 1901
Disambiguated annotations:
qaPairs: question: What year did blood transfusions become safer thanks to Karl Landsteiner?
answer: 1901
question: With what event did blood transfusions become safer and why in 1901?
answer: Karl Landsteiner discovered three human blood groups (O, A, and B)
question: What year did blood transfusions become safer thanks to Rhesus blood system discovery?
answer: 1937–40
question: With what ?event did blood transfusions become safer and why in 1937-1940?
answer: discovered the Rhesus blood group system, which was found to be the cause of the majority of transfusion reactions