X0607 3/A 2026-05-01 2026-05-04 0 0000310158 Merck & Co., Inc. MRK 0002126478 Maraldo David R. false 126 EAST LINCOLN AVENUE RAHWAY NJ 07065 1 EVP & Pres. MMD Common Stock 17819.434 D Common Stock - 401(k) Plan 8359.14 I By 401 (k) Restricted Stock Unit 2024-05-02 2026-05-02 Common Stock 552 D Restricted Stock Unit 2025-04-30 2027-04-30 Common Stock 581 D Restricted Stock Unit 2026-04-29 2028-04-29 Common Stock 2361 D Stock Option (Right to Buy) 73.73 2022-05-04 2031-05-03 Common Stock 9465 D Stock Option (Right to Buy) 87.10 2023-05-03 2032-05-02 Common Stock 9709 D Stock Option (Right to Buy) 117.89 2024-05-02 2033-05-01 Common Stock 8990 D Stock Option (Right to Buy) 129.22 2025-04-30 2034-04-29 Common Stock 8789 D Stock Option (Right to Buy) 84.71 2026-04-29 2035-04-28 Common Stock 8060 D These restricted stock units vest and are distributed as shares of Merck & Co., Inc. common stock in three equal installments on 5/2/2024, 5/2/2025, and 5/2/2026. Each restricted stock unit represents a contingent right to receive one share of Merck & Co., Inc. common stock. These restricted stock units vest and are distributed as shares of Merck & Co., Inc. common stock in three equal installments on 4/30/2025, 4/30/2026, and, 4/30/2027. These restricted stock units vest and are distributed as shares of Merck & Co., Inc. common stock in three equal installments on 4/29/2026, 4/29/2027, and, 4/29/2028. The options became exercisable in equal installments in on 5/4/2022, 5/4/2023, and 5/4/2024. The options became exercisable in equal installments on 5/3/2023, 5/3/2024, and 5/3/2025. The options vest and become exercisable in equal installments on 5/2/2024, 5/2/2025, and 5/2/2026. The options vest and become exercisable in equal installments on 4/30/2025, 4/30/2026, and 4/30/2027. The options vest and become exercisable in equal installments on 4/29/2026, 4/29/2027, and 4/29/2028. This amendment is being filed solely to: (a) update footnote 6 to correct the schedule on which the applicable options became exercisable and (b) attach a Power of Attorney that was inadvertently omitted from the original filing. Exhibit 24: Power of Attorney is attached. /s/ Kelly E. W. Grez as Attorney-in-Fact for David R. Maraldo 2026-05-05