[1] Halloran studied physics and philosophy of mathematics for two years as an undergraduate at Case Western Reserve University, from 1968 to 1970,[2] before leaving school to join the counterculture movement in San Francisco.
[3] Deciding to study medicine, she returned to school,[3] completing a bachelor's degree in general science at the University of Oregon in 1972.
[2] In that program, she rekindled her interest in mathematical modeling,[3] and she stayed at Harvard as a graduate student, earning a D.Sc.
In 2009, she founded the Summer Institute in Statistics and Modeling in Infectious Diseases at the University of Washington, and continues to serve as its director.
[3] She is a long-term collaborator with University of Florida researcher Ira Longini, with whom she studies the spread of influenza.