144 0001421339 XXXXXXXX LIVE 0000310158 MERCK & CO. INC. 001-06571 126 East Lincoln Avenue Rahway NJ 07065 908-740-4000 RICHARD ROBERT DELUCA JR. Officer Common Morgan Stanley Smith Barney LLC Executive Financial Services

1 New York Plaza 38th Floor New York NY 10004

43823 4602668.34 2534023084 11/08/2023 NYSE Common 10/08/2019 Restricted stock vesting under a registered plan Issuer N 470 10/08/2019 Not Applicable Common 10/13/2020 Restricted stock vesting under a registered plan Issuer N 499 10/13/2020 Not Applicable Common 01/13/2021 Restricted stock vesting under a registered plan Issuer N 517 01/13/2021 Not Applicable Common 07/12/2021 Restricted stock vesting under a registered plan Issuer N 965 07/12/2021 Not Applicable Common 10/13/2021 Restricted stock vesting under a registered plan Issuer N 926 10/13/2021 Not Applicable Common 01/12/2022 Restricted stock vesting under a registered plan Issuer N 1001 01/12/2022 Not Applicable Common 04/08/2020 Restricted stock vesting under a registered plan Issuer N 669 04/08/2020 Not Applicable Common 02/24/2022 Restricted stock vesting under a registered plan Issuer N 2152 02/24/2022 Not Applicable Common 04/12/2022 Restricted stock vesting under a registered plan Issuer N 1063 04/12/2022 Not Applicable Common 07/13/2022 Restricted stock vesting under a registered plan Issuer N 989 07/13/2022 Not Applicable Common 10/12/2022 Restricted stock vesting under a registered plan Issuer N 1029 10/12/2022 Not Applicable Common 01/12/2023 Restricted stock vesting under a registered plan Issuer N 895 01/12/2023 Not Applicable Common 01/23/2023 Restricted stock vesting under a registered plan Issuer N 15628 01/23/2023 Not Applicable Common 04/13/2023 Restricted stock vesting under a registered plan Issuer N 992 04/13/2023 Not Applicable Common 10/06/2023 Restricted stock vesting under a registered plan Issuer N 1093 10/06/2023 Not Applicable Common 02/25/2019 Restricted stock vesting under a registered plan Issuer N 13507 02/25/2019 Not Applicable Common 04/08/2019 Restricted stock vesting under a registered plan Issuer N 479 04/08/2019 Not Applicable Common 07/09/2019 Restricted stock vesting under a registered plan Issuer N 460 07/09/2019 Not Applicable Common 01/09/2020 Restricted stock vesting under a registered plan Issuer N 489 01/09/2020 Not Applicable Y 11/08/2023 /s/ Robert R. DeLuca