Merck & Co. was created in its modern expanded form by the 2009 merger of Merck & Co. and Schering-Plough.
Merck announced the transaction in March 2009, and it closed in November of that year. The deal, valued at roughly $41 billion, combined Merck’s prescription medicines and vaccine businesses with Schering-Plough’s pharmaceutical portfolio and international reach.
The surviving company kept the Merck name in the United States and Canada. Outside those markets, the business generally uses the name MSD because another company, Merck KGaA of Germany, owns rights to the Merck name in many countries. This naming difference is a frequent source of confusion in pharmaceutical trivia.
The combined company inherited products and research programs from both businesses, including medicines in areas such as cardiovascular disease, infectious disease, and immunology. The transaction was separate from Merck’s earlier 2004 acquisition of another company also called Merck, which is now known as EMD Serono in the United States.