MRK: Leadership change

Item 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers. (d) Incorporated by reference is a press release issued by Merck & Co., Inc. (the “Company”) on October 13, 2026, attached as Exhibit 99.1, announcing the election of Paul J. Diaz to the Company’s Board of Directors (the “Board”), effective November 1, 2026. The Board appointed Mr. Diaz as a member of both the Audit Committee and the Research Committee of the Board. For his service on the Board, Mr. Diaz will receive compensation as a non-employee director in accordance with the Company’s non-employee director compensation practices described under the “Director Compensation” section of the Company’s definitive proxy statement on Schedule 14A filed with the Securities and Exchange Commission on April 8, 2026. Mr. Diaz has no arrangements or understandings with any other person pursuant to which he was elected to the Board, nor does he have a relationship or related transaction with the Company that would require disclosure pursuant to Item 404(a) of Regulation S-K of the Securities and Exchange Commission in connection with his appointment as a director of the Company. Item 9.01. Financial Statements and Exhibits. (d) Exhibits Exhibit 99.1 Press release issued October 13, 2026 Exhibit 104 Cover Page Interactive Data File (embedded within the Inline XBRL document) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Merck & Co., Inc. Date: October 13, 2026 By: /s/ Kelly E. W. Grez Kelly E. W. Grez Corporate Secretary