The Rockefeller Foundation required all staff to retire at the age of sixty-five, and in accordance with that rule, Sawyer left the IHD in August 1944. He did not retire, but accepted the position of Director of Health for the United Nations Relief and Rehabilitation Administration (UNRRA). UNRRA had been established in 1943 to help provide food, shelter, and clothing, and to restore agriculture, industry, and public health services to civilians as the Axis forces retreated. The Health Division was staffed by about 1,400 physicians, nurses, dentists, and sanitary engineers, recruited from more than 35 countries. Many were on loan from the U.S. Public Health Service and the British Ministry of Health. With many national health departments handicapped or destroyed by the war, there was a great shortage of personnel, materials, equipment, transport, and facilities essential to the maintenance of medical care and public health. Likewise, health care education had been disrupted in many countries. The UNRRA Health Division helped national health authorities prevent or contain war-engendered epidemics (including typhus fever, diphtheria, tuberculosis, and cholera), restore national health departments, and determine the medical and sanitary supplies required to replace losses through destruction, looting, and restricted access during the war. It also provided medical and sanitary personnel for refugee camps in some areas, and provided professional public health training in many of the assisted countries. In the three years of its operation, Sawyer's division became the largest international health organization ever seen. It spent close to $168,000,000, much of it for procurement and shipment of medical and sanitation supplies--vaccines, drugs, chemicals, hospital equipment, and laboratory supplies.
The UNRRA formed a much-needed bridge between the earlier pre-war international health organizations, such as that of the League of Nations, and the post-war World Health Organization (WHO). Sawyer was part of the planning committee that met for several weeks in June 1946 to work out the structure for WHO. In 1947, with much of the post-war clean-up accomplished or well underway, the remaining functions of the UNRRA Health Division were handed over to WHO, and UNRRA was dissolved.
Sawyer's last large project was the Fourth International Congress on Tropical Medicine and Malaria, held in May 1948, for which he served as executive secretary and secretary general. He and Mrs. Sawyer closed up their house in Washington in December 1948, and traveled in Mexico and Guatemala for several months. After making visits to family and friends in the eastern U.S., they drove across the country to California, where they settled in Berkeley in June 1949. For the next several years, Sawyer kept busy with friends and family, travels in California, gardening, symphonies and operas, and photography. He remained active in his professional organizations and stayed in touch with his many public health colleagues. His health began to deteriorate, however and he was diagnosed with congestive heart failure in 1950. He died on November 12, 1951.