He completed his fellowships in surgery between 1990-1998 in London hospitals (Watford, St. Thomas, King’s College, Royal Free Hospital) with special interest in vascular, cancer and liver transplantation surgery.
[citation needed] Back to Lebanon in 1991, he chaired the division of General Surgery and was appointed as the Director of the Liver Transplant and Hepato-Pancreatico-Biliary Unit at the American University of Beirut Medical Center where he performed the first liver transplantation surgery in the region and pioneered many other major surgical techniques.
[2] In the period between 2004-2010, Professor Khalifeh was named in five successive governments as the minister of Public Health of Lebanon.
In addition to his public duties, Professor Khalifeh kept practicing surgeries at AUB-Medical Center, teaching students, training residents and producing research.
Under his terms as Minister of Health, Lebanon launched a network of accredited primary health care centers in addition to opening over 20 public hospitals in the country, a new registry for quality and pricing of pharmaceuticals in Lebanon was created, a health reform plan that guarantees a mandatory public national health insurance system to every citizen was instituted, and the official National Cancer Registry (NCR) in Lebanon was launched.