The antibody formation theory gave Jerne international recognition and in 1956 Jerne went to work for the World Health Organization in Geneva, where he served as the Head of the Sections of Biological Standards and of Immunology. He held this post for six years until moving to the United States and the University of Pittsburgh in 1962 to work as Professor of Microbiology and Chairman of the Department of Microbiology for four years. Jerne continued to do work for the World Health Organization as a member of the Expert Advisory Panel of Immunology from 1962 and onwards.