How was Charles Jules Henri Nicolle awarded the Noble Prize in Physiology or Medicine?

Name: Charles Jules Henri Nicolle.
Country: France.
Date of Birth: 21 September 1866.
Died: 28 February 1936.
Education: University of Paris.
Subjects Of Study: Body louse carrier typhus.
Known as: Epidemic typhus.
Noble Prize Year: Nobel Prize for Peace in 1928, for his discovery that typhus is transmitted by the body louse.