Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionGrantham, Mayo, Van Otterloo & Co. LLC
Latest Disclosed Ownership7,013,777 shares
Latest Disclosed Value $ 843,687,399
Grantham, Mayo, Van Otterloo & Co. LLC reports 2.09% increase in ownership of MRK / Merck & Co., Inc.

On May 14, 2026 - Grantham, Mayo, Van Otterloo & Co. LLC filed a 13F-HR form disclosing ownership of 7,013,777 shares of Merck & Co., Inc. (MX:MRK) valued at $843,687,399 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 6,870,145 shares of Merck & Co., Inc.. This represents a change in shares of 2.09% during the quarter.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-14 2026-03-31 13F MERCK COM 58933Y105 7,013,777 143,632 2.09 843,687 16.67 2.1580
2026-02-17 2025-12-31 13F MERCK COM 58933Y105 6,870,145 244,795 3.69 723,152 30.05 1.8485
2025-11-13 2025-09-30 13F MERCK COM 58933Y105 6,625,350 155,777 2.41 556,066 8.58 1.5682
2025-08-13 2025-06-30 13F MERCK COM 58933Y105 6,469,573 -217,023 -3.25 512,131 -14.67 1.5411
2025-05-14 2025-03-31 13F MERCK COM 58933Y105 6,686,596 521,325 8.46 600,189 -2.14 1.8923
2025-02-13 2024-12-31 13F MERCK COM 58933Y105 6,165,271 253,227 4.28 613,321 -8.65 1.9951
2024-11-13 2024-09-30 13F MERCK COM 58933Y105 5,912,044 583,752 10.96 671,372 1.78 2.1042
2024-08-13 2024-06-30 13F MERCK COM 58933Y105 5,328,292 601,234 12.72 659,643 5.76 2.2279
2024-05-14 2024-03-31 13F MERCK COM 58933Y105 4,727,058 701,200 17.42 623,735 42.11 2.2667
2024-02-13 2023-12-31 13F MERCK COM 58933Y105 4,025,858 -3,058 -0.08 438,899 5.82 1.9368
2023-11-13 2023-09-30 13F MERCK COM 58933Y105 4,028,916 411,073 11.36 414,777 -0.64 1.9591
2023-08-14 2023-06-30 13F MERCK COM 58933Y105 3,617,843 564,296 18.48 417,463 28.50 1.9326
2023-05-12 2023-03-31 13F MERCK COM 58933Y105 3,053,547 -89,264 -2.84 324,867 -6.83 1.6525
2023-02-13 2022-12-31 13F MERCK COM 58933Y105 3,142,811 36,156 1.16 348,695 30.33 1.8575
2022-11-10 2022-09-30 13F MERCK COM 58933Y105 3,106,655 -3,300 -0.11 267,545 -5.64 1.5437
2022-08-12 2022-06-30 13F MERCK COM 58933Y105 3,109,955 -737,348 -19.17 283,535 -10.18 1.5358
2022-05-13 2022-03-31 13F MERCK COM 58933Y105 3,847,303 59,929 1.58 315,671 8.75 1.5231
2022-02-11 2021-12-31 13F MERCK COM 58933Y105 3,787,374 77,162 2.08 290,264 4.16 1.3942
2021-11-12 2021-09-30 13F MERCK COM 58933Y105 3,710,212 138,334 3.87 278,674 0.32 1.3785
2021-08-12 2021-06-30 13F MERCK COM 58933Y105 3,571,878 291,195 8.88 277,785 9.84 1.3858
2021-05-13 2021-03-31 13F MERCK & CO. CO 58933Y105 3,280,683 254,063 8.39 252,908 2.15 1.3815
2021-02-12 2020-12-31 13F MERCK & CO. COM 58933Y105 3,026,620 11,956 0.40 247,578 -0.99 1.5208
2020-11-13 2020-09-30 13F MERCK & CO. COM 58933Y105 3,014,664 55,060 1.86 250,066 9.26 1.7797
2020-08-13 2020-06-30 13F MERCK & CO. COM 58933Y105 2,959,604 -87,498 -2.87 228,866 -2.38 1.6993
2020-05-14 2020-03-31 13F MERCK & CO. COM 58933Y105 3,047,102 -789,823 -20.58 234,444 -32.82 1.9550
2020-02-13 2019-12-31 13F MERCK COM 58933Y105 3,836,925 -74,970 -1.92 348,968 5.97 2.3306
2019-11-13 2019-09-30 13F MERCK COM 58933Y105 3,911,895 191,749 5.15 329,303 5.57 2.2845
2019-08-13 2019-06-30 13F MERCK COM 58933Y105 3,720,146 639,128 20.74 311,934 21.73 2.1954
2019-05-14 2019-03-31 13F MERCK COM 58933Y105 3,081,018 -468,524 -13.20 256,248 -5.52 1.8429
2019-02-13 2018-12-31 13F MERCK COM 58933Y105 3,549,542 -423,445 -10.66 271,221 -3.77 2.1657
2018-11-14 2018-09-30 13F MERCK COM 58933Y105 3,972,987 39,511 1.00 281,844 18.04 1.9096
2018-08-14 2018-06-30 13F MERCK COM 58933Y105 3,933,476 1,158,638 41.76 238,762 57.97 1.6952
2018-05-15 2018-03-31 13F MERCK COM 58933Y105 2,774,838 2,279,670 460.38 151,145 442.46 0.9246
2018-02-14 2017-12-31 13F MERCK COM 58933Y105 495,168 420,368 561.99 27,863 481.81 0.1644
2017-11-14 2017-09-30 13F MERCK COM 58933Y105 74,800 68,500 1,087.30 4,789 1,085.40 0.0280
2017-08-14 2017-06-30 13F MERCK COM 58933Y105 6,300 -1,300 -17.11 404 -16.36 0.0022
2017-05-15 2017-03-31 13F MERCK COM 58933Y105 7,600 -6,100 -44.53 483 -40.15 0.0027
2017-02-13 2016-12-31 13F MERCK COM 58933Y105 13,700 6,200 82.67 807 72.44 0.0043
2016-11-10 2016-09-30 13F MERCK COM 58933Y105 7,500 7,500 0.00 468 0.0022
2016-05-13 2016-03-31 13F MERCK & CO INC COM 58933Y105 0 -4,200 -100.00 0 -100.00
2016-02-12 2015-12-31 13F MERCK & CO INC COM 58933Y105 4,200 0 0.00 222 7.25 0.0008
2015-11-13 2015-09-30 13F MERCK & CO INC COM 58933Y105 4,200 -2,300 -35.38 207 -44.05 0.0007
2015-08-13 2015-06-30 13F MERCK & CO INC COM 58933Y105 6,500 -2,422 -27.15 370 -27.88 0.0012
2015-05-14 2015-03-31 13F MERCK & CO INC COM 58933Y105 8,922 -4,100 -31.49 513 -30.68 0.0015
2015-02-13 2014-12-31 13F MERCK & CO INC COM 58933Y105 13,022 -105,868 -89.05 740 -89.50 0.0020
2014-11-13 2014-09-30 13F MERCK & CO INC COM 58933Y105 118,890 -222,081 -65.13 7,048 -64.27 0.0187
2014-08-13 2014-06-30 13F MERCK & CO INC COM 58933Y105 340,971 -2,178,107 -86.46 19,725 -86.21 0.0536
2014-05-14 2014-03-31 13F MERCK & CO INC COM 58933Y105 2,519,078 -7,146,258 -73.94 143,008 -70.44 0.3730
2014-02-13 2013-12-31 13F MERCK & CO INC COM 58933Y105 9,665,336 -3,625,772 -27.28 483,750 -23.55 1.1740
2013-11-14 2013-09-30 13F MERCK & CO INC COM 58933Y105 13,291,108 342,980 2.65 632,790 5.21 1.6679
2013-08-13 2013-06-30 13F MERCK & CO INC COM 58933Y105 12,948,128 12,948,128 601,441 1.5662
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.