X0508 4 2026-02-04 0000310158 Merck & Co., Inc. MRK 0001363076 Davis Robert M MERCK & CO., INC. 126 EAST LINCOLN AVENUE RAHWAY NJ 07065 1 1 Chairman, CEO & President 0 Common Stock 2026-02-04 4 S 0 14972 117.3796 D 476063.757 D Common Stock 2026-02-04 4 S 0 32462 118.3513 D 443601.757 D The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $116.9600 to $117.9500, inclusive. The reporting person undertakes to provide to Merck & Co., Inc., any security holder of Merck & Co., Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth above in this footnote. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $118.0000 to $118.7100, inclusive. The reporting person undertakes to provide to Merck & Co., Inc., any security holder of Merck & Co., Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth above in this footnote. /s/ Kelly E. W. Grez as Attorney-in-Fact for Robert M. Davis 2026-02-06