Merck & Co. Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant

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Notice of Annual Meeting

of Shareholders

To Shareholders:

You are invited to the Annual Meeting of Shareholders of Merck & Co., Inc., Rahway, NJ, U.S.A. (the “Company”) on Tuesday, May 27, 2025, at 9:00 a.m. (Eastern Time) via Webcast atwww.virtualshareholdermeeting.com/MRK2025(the “2025 Annual Meeting”).

The purposes of the meeting are to:

1. Elect the 13 Director nominees named in this proxy statement;

2. Consider and act upon a proposal to approve, bynon-binding advisory vote, the compensation of our Named Executive Officers;

3. Consider and act upon a proposal to ratify the appointment of PricewaterhouseCoopers LLP as the Company’s independent registered public accounting firm for 2025;

4. Consider and act upon a shareholder proposal regarding a human rights impact assessment, if properly presented at the meeting;

5. Consider and act upon a shareholder proposal regarding a tax transparency report, if properly presented at the meeting;

6. Consider and act upon a shareholder proposal to revisit DEI goals in executive pay incentives, if properly presented at the meeting;

7. Consider and act upon a shareholder proposal regarding a report on civil liberties in advertising services, if properly presented at the meeting; and

8. Transact such other business as may properly come before the meeting.

By order of the Board of Directors,

Kelly E. W. Grez

Corporate Secretary

Vote Right Away—Advance voting methods and deadlines

We encourage all shareholders of record to read this proxy statement with care and vote right away using any of the following methods, even if they intend to attend the 2025 Annual Meeting. In all cases, have your proxy card or voting instruction form in hand and follow the instructions.

Only shareholders listed on the Company’s records at the close of business on March 28, 2025 are entitled to vote.

The Company began distributing its Notice of Internet Availability of Proxy Materials, proxy statement, the Company’s Annual Report on Form 10-K for the year ended December 31, 2024 (the “202410-K”) and proxy card/voting instruction form, as applicable, to shareholders and to employee benefit and stock purchase plan participants on April 9, 2025.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE ANNUAL MEETING OF SHAREHOLDERS TO BE HELD ON MAY 27, 2025:

The Notice of Annual Meeting of Shareholders, proxy statement and the 2024 Annual Report on Form 10-K are available free of charge atwww.proxyvote.com.

The principal executive offices of the Company are located at 126 East Lincoln Avenue, Rahway, N.J. 07065 U.S.A.

• The telephone and internet voting facilities will close at 11:59 p.m. Eastern Time on May 26, 2025.

** You will need the 16-digit control number included on your proxy card, voting instruction form or Notice of Internet Availability of Proxy Materials.

If your shares are held in a stock brokerage account or by a bank or other nominee, your ability to vote by telephone or over the internet depends on your broker’s voting process. Please follow the directions provided to you by your broker, bank, or nominee.

Dear Fellow Shareholders,

Across our Company, 2024 was another year of significant advancement, innovation, and focus on patient delivery. I am inspired by our progress in developing and delivering transformative human and animal health medicines and vaccines to help save and improve lives around the world. We have continued to execute on our strategic priorities, launching important new products that bring clinical value to patients. We have also advanced key clinical programs in our robust early- and late-phase pipeline, while expanding and diversifying through business development when science and value align. And, we have continued to grow our footprint in the United States and beyond, reflecting substantial long-term investments in manufacturing and research and development. Our Company has allocated over $12 billion toward U.S. capital investment since 2018, and we expect to invest over $9 billion more by the end of 2028, which will create more jobs in the U.S.

We are anchored by a robust set of commercial products addressing important medical needs, and I am pleased that we’re rapidly moving to a future with a much more diversified portfolio. Today, we have 20 new potential growth drivers, almost all of which have blockbuster potential. Over the past three years, the number of candidates in late-phase development has nearly tripled across a broad range of therapeutic areas and new modalities. Based on this progress, we now see over $50 billion of potential revenue opportunities from our late-stage pipeline alone by the mid-2030s. Our science-led strategy is working, and our team is moving with speed and rigor to deliver value for patients, society, and all of our stakeholders.

In oncology, we have diversified our pipeline and are well positioned to maintain our leadership in this critical and competitive area. In 2024, we marked 10 years since KEYTRUDA became the first anti-PD-1 therapy approved in the U.S. Globally, more than 2.6 million patients have been prescribed KEYTRUDA, and that number continues to grow. To date, the U.S. Food and Drug Administration (FDA) has approved KEYTRUDA for 41 indications across 18 types of cancer. Our studies of KEYTRUDA-based regimens in earlier-stage cancers have supported nine indications, with four Phase 3 studies in earlier settings demonstrating a significant overall survival benefit. Importantly, our Biologics License Application (BLA) for subcutaneous

pembrolizumab and berahyaluronidase alfa is under review with the FDA. If approved, it has the potential to improve the patient experience while increasing access and saving time for patients and health care providers compared to intravenous administration.

We also continue to make progress across our broad oncology portfolio and comprehensive pipeline of antibody-drug conjugates (ADCs), precision targeted small molecules, T-cell engagers, as well as the individualized neoantigen therapy through our collaboration with Moderna. WELIREG, our HIF-2 alpha inhibitor approved in the U.S., recently gained its first approvals in China and Europe. In addition, the FDA granted Breakthrough Therapy designation to sacituzumab tirumotecan (sac-TMT), our investigational TROP-2-directed ADC being developed through a collaboration with Kelun-Biotech, for the treatment of certain patients with previously treated advanced non-small cell lung cancer.

The treatment of cardiometabolic diseases is another area we are seeing significant momentum and long-term potential. During 2024, we successfully launched WINREVAIR, a first-in-class activin signaling inhibitor for the treatment of adults with pulmonary arterial hypertension. WINREVAIR has achieved several important regulatory milestones and is now approved in more than 40 countries globally. The clinical development program for WINREVAIR continues to yield important data, including positive results from the Phase 3 ZENITH trial, which was stopped early due to overwhelming efficacy at the interim analysis, and supports the potential of WINREVAIR to be practice-changing in the management of this progressive and debilitating disease. In addition, our investigational oral PCSK9 inhibitor, enlicitide decanoate for the treatment of hypercholesterolemia, is being evaluated in multiple Phase 3 trials with anticipated readouts for some of the trials in 2025. Of note, despite widely available statin treatments, millions of people globally are not able to lower their low-density lipoprotein (LDL) cholesterol to guideline-recommended levels, leaving them at risk for cardiac events.

Vaccines play a critical role in global public health, helping to prevent a variety of infectious diseases. In vaccines and infectious diseases, we achieved several clinical, regulatory and commercial milestones. For example, the FDA accepted the BLA for clesrovimab, an investigational prophylactic long-acting monoclonal antibody designed to protect infants from respiratory syncytial virus (RSV) during their first RSV season. RSV is a leading cause of infant hospitalizations in the U.S. If approved, clesrovimab has the potential to be the first and only immunization designed to protect healthy and certain at-risk infants with the same single dose regardless of weight for the duration of their first RSV season.

In addition, we continue to build on our proud legacy of developing important innovations for both the treatment and prevention of HIV infection. We recently announced

positive results from two Phase 3 trials evaluating the once-daily, oral combination of doravirine and islatravir in adults with HIV infection who are virologically suppressed on different antiretroviral therapy regimens. Additionally, we are encouraged by the combination of lenacapavir and islatravir, through our collaboration with Gilead currently in Phase 3 studies, and MK-8527 as a potentially important once-monthly oral option for pre-exposure prophylaxis (PrEP), which we expect to advance to Phase 3 in 2025.

Though we experienced challenging market dynamics for GARDASIL and GARDASIL 9 in China, we believe this market continues to represent a potential long-term opportunity for the vaccine, especially following approval for the use of GARDASIL in males ages 9-26 in China. Demand for GARDASIL and GARDASIL 9 remains robust in other major regions, and we expect strong growth in those regions in the future. We take pride in the role GARDASIL and GARDASIL 9 are playing globally in helping to protect males and females 9 to 45 years of age from certain human papillomavirus (HPV)-related cancers and diseases. And in pneumococcal disease, we are excited by the promising launch of CAPVAXIVE in the U.S. and its early progress with global approvals. Reinforcing our confidence in its potential, in 2024, the U.S. Centers for Disease Control’s Advisory Committee on Immunization Practices recommended CAPVAXIVE for adults ages 50 and older.

In addition, we see important opportunities in both immunology and ophthalmology. We are conducting Phase 3 studies of tulisokibart, a potential first-in-class treatment for Crohn’s disease and ulcerative colitis. And following our acquisition of EyeBio, we have initiated a Phase 3 study of MK-3000 in patients with diabetic macular edema and intend to evaluate it in patients with neovascular age-related macular degeneration as well.

Our Animal Health business achieved another year of strong performance driven by our Companion Animal and Livestock portfolios. We also acquired the aqua business of Elanco Animal Health, helping establish our Company as a leader in this important production animal category. We are well positioned in Animal Health to continue to drive above-market growth in 2025, driven by new launches including the injectable formulation of BRAVECTO and a next-

generation dermatology product in the Companion Animal segment. Beyond the 2025 launches, a strong Livestock and Companion Animal pipeline positions Animal Health for future growth opportunities.

Business development remains a priority and a key component of our strategy to augment, complement, and diversify our pipeline. In 2024, we executed over 70 external licenses, collaborations, and acquisitions. These include our acquisition of the bispecific antibody MK-1045, with potential applications in both oncology and immunology, from Curon Biopharmaceutical, and our exclusive global licenses with LaNova Medicines and Hansoh Pharma, for MK-2010, an investigational anti-PD-1/VEGF bispecific antibody, and MK-4082, an oral GLP-1 receptor agonist, respectively. Since 2021, we have invested approximately $40 billion in establishing an increasingly diverse pipeline that spans multiple therapeutic areas and modalities targeting a wide range of disease indications.

For more than 130 years, our Company has been dedicated to operating responsibly. Expanding and enabling access to our medicines and vaccines for the hundreds of millions of people around the world who depend on us is both a great responsibility and a profound privilege. In 2024, we reached nearly half a billion people globally with our medicines and vaccines through commercial channels, clinical trials, voluntary licensing, and product donations. We continue to donate medicines and vaccines through our U.S. patient assistance program, as well as disaster relief and humanitarian aid initiatives, aimed at supporting underserved populations worldwide.

As we navigate 2025, I have more confidence than ever in our ability to deliver sustainable, long-term value. Fueled by our relentless focus on leading-edge science, we will continue to keep patients at the center of everything we do and deliver innovative solutions that address some of the world’s most serious global health challenges, while also creating value for our shareholders.

Thank you for your confidence and support of our Company. We encourage you to participate in the Annual Meeting by exercising your right to vote.

A Message from the Independent Lead Director

Dear Fellow Shareholders,

On behalf of the Board, I would like to thank you for your investment and support. We are committed to representing our shareholders through dedicated, independent oversight, and it is my privilege to serve as Lead Director.

Board Oversight

As you read in the letter from our Chairman and CEO, Robert M. Davis, in 2024, the Company continued to make progress to develop and deliver transformative human and animal health medicines and vaccines to help save and improve lives around the world. The Board remained focused on ensuring management delivers on its responsibilities to drive sustainable, long-term value, drawing on our unique experiences to do so. At meetings, the Board engages the Company’s senior leaders in robust discussions about corporate strategy, risks, and opportunities, providing guidance, and monitoring implementation in areas such as research and development, capital allocation, operating results, human capital management, and global manufacturing.

Board Refreshment

As a Board, we are committed to ensuring that we have the collective skills, experience, and perspectives that, taken together, can provide effective oversight with respect to the Company’s current and future global business and strategic initiatives, opportunities, and challenges. We also look to balance fresh perspectives with the insights of longer-tenured directors. Six independent Directors have joined the Board since 2020, including most recently, Surendralal “Lal” Karsanbhai, who joined our Board in January 2025. As President and CEO of Emerson Electric, Lal brings to the Board extensive business and operational expertise with a strong global perspective.

Our annual self-evaluation process helps us identify ways to continue to enhance the overall effectiveness of the Board and its committees. It also gives us the opportunity to discuss other important topics through feedback from each of our Directors that is then considered by the full Board. Among other things, Directors provide feedback on Board composition, the Board’s leadership and structure, and the level and quality of Director contributions.

Shareholder Engagement

Regular engagement with our shareholders is important so that we may better understand your perspectives. In 2024, the Company continued its robust and proactive shareholder engagement program. I personally participated in several engagements together with members of management, and I appreciated the opportunity to share the Board’s perspective and hear directly from shareholders on their priorities. Topics included corporate strategy, capital allocation, risk oversight, and board composition. The Board discussed feedback received from investors as part of these engagements, and this feedback has helped shape the Company’s policies, practices, and disclosures.

Once again, we appreciate your investment in the Company and support for the Board. We remain committed to serving you and the patients around the world that depend on the Company’s life-saving work.