Merck & Co., Inc. (MRK) vs UnitedHealth Group Incorporated (UNH)

Merck & Co., Inc. develops pharmaceutical products across multiple therapeutic areas, including cardiometabolic disorders, oncology, and infectious diseases. In cancer treatment, its immuno-oncology portfolio, led by Keytruda, represents a significant driver of total revenue. The company also maintains a strong vaccines business focused on preventing pediatric illnesses, alongside Gardasil for human papillomavirus. In addition, Merck markets animal health products. Geographically, 47% of the company’s sales come from its U.S. human health segment, which includes pharmaceuticals and vaccines.

UnitedHealth Group Incorporated is among the world’s largest private health insurers, providing medical benefits to roughly 51 million members globally as of December 2025, including about 1 million outside the United States. A leading provider of employer-sponsored, self-directed, and government-supported health plans, the company has built substantial scale in the medical insurance market. In addition to its core insurance operations, UnitedHealth’s Optum businesses expand its reach across healthcare services, spanning pharmacy benefits, outpatient care, and analytics for affiliated organizations and third-party clients.