Jeffrey was the Vice Dean of Medical Education at the University of Ottawa (1996-2001), the President of the Medical Council of Canada (1999-2000), the President of the College of Physicians and Surgeons of Ontario (2006-2007), and the President of Canadian Medical Association (2010-2011). He also served as Senior Medical Officer for Correction Services Canada (2011-2014), as well as the Chief of Staff at The Ottawa Hospital (2008-2017). In 2001, he helped establish Ottawa Inner City Health, which works to improve access to health care for people who are chronically homeless. He has also been involved in educational and health initiatives in Bangladesh, Africa, and the Balkans.
Jeffrey holds a Bachelor of Science from the University of Toronto, a Master of Education from the University of Western of Ontario, and a Doctorate in Medicine from Queen's University. He later received a speciality certification in Internal Medicine through the Royal College of Physicians and Surgeons of Canada. He is also the recipient of several national and international awards, including the Order of Canada.