Between 1914 and 1972 Connaught Medical Research Laboratories (as it was known after 1946) was a self-supporting, non-commercial part of the University of Toronto. It was sold by the U. of T. in 1972 to the Canadian Development Corporation (CDC). In 1989 Connaught Laboratories Limited (as it was known after 1972) was sold to Institut Mérieux of Lyon, France, and soon became part of the global Pasteur Mérieux Connaught (PMC) organization. PMC's parent company, Rhone Poulenc of France merged with Hoechest of Germany in December 1999 to create Aventis, the vaccine division of which (the former PMC) becoming known as Aventis Pasteur.

1989: Connaught Laboratories (Canada) joined Pasteur Mérieux (France) to form Pasteur Mérieux Connaught.
1999: Pasteur Mérieux Connaught becomes Aventis Pasteur. 
Aventis Pasteur MSD was formed from an alliance between Aventis Pasteur and Merck & Co., Inc.

Connaught was the first company to mass produce insulin during the 1920s and a large scale producer of the first Salk polio vaccine in the 1950s. In 1978, Connaught acquired the research and production facilities of the Salk Institute in Swiftwater, Pennsylvania, and established its U.S. subsidiary, Connaught Laboratories Inc.