Merck & Co., Inc.
BG ˙ BUL ˙ US58933Y1055
SecurityBG:6MK / Merck & Co., Inc.
InstitutionJanus Henderson Group Plc
Latest Disclosed Ownership2,880,199 shares
Latest Disclosed Value $ 346,466,846
Janus Henderson Group Plc reports 52.78% increase in ownership of 6MK / Merck & Co., Inc.

On May 18, 2026 - Janus Henderson Group Plc filed a 13F-HR/A form disclosing ownership of 2,880,199 shares of Merck & Co., Inc. (BG:6MK) valued at $346,466,846 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 1,885,140 shares of Merck & Co., Inc.. This represents a change in shares of 52.78% 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)
2026-05-18 2026-03-31 13F/A-1 MERCK COM 58933Y105 2,880,199 995,059 52.78 346,467 74.58 0.0584
2026-05-15 2026-03-31 13F MERCK COM 58933Y105 2,880,199 995,059 52.78 346,467 74.58 0.0643
2026-02-17 2025-12-31 13F MERCK COM 58933Y105 1,885,140 -230,401 -10.89 198,458 11.79 0.0889
2025-11-14 2025-09-30 13F MERCK COM 58933Y105 2,115,541 1,573,424 290.24 177,526 313.97 0.0810
2025-08-14 2025-06-30 13F MERCK COM 58933Y105 542,117 -2,223,249 -80.40 42,884 -82.62 0.0210
2025-05-15 2025-03-31 13F MERCK COM 58933Y105 2,765,366 -3,099,139 -52.85 246,750 -57.71 0.1353
2025-02-14 2024-12-31 13F MERCK COM 58933Y105 5,864,505 -2,905,121 -33.13 583,418 -41.42 0.2965
2024-11-14 2024-09-30 13F MERCK COM 58933Y105 8,769,626 -1,921,052 -17.97 995,888 -24.76 0.5097
2024-08-14 2024-06-30 13F MERCK COM 58933Y105 10,690,678 229,514 2.19 1,323,550 -4.11 0.7088
2024-05-15 2024-03-31 13F MERCK COM 58933Y105 10,461,164 -1,595,753 -13.24 1,380,276 5.01 0.7529
2024-02-14 2023-12-31 13F MERCK COM 58933Y105 12,056,917 -273,178 -2.22 1,314,473 3.54 0.7840
2023-11-14 2023-09-30 13F MERCK COM 58933Y105 12,330,095 -1,154,477 -8.56 1,269,510 -18.40 0.8313
2023-08-14 2023-06-30 13F MERCK COM 58933Y105 13,484,572 -172,415 -1.26 1,555,825 7.08 0.9676
2023-05-15 2023-03-31 13F MERCK COM 58933Y105 13,656,987 266,757 1.99 1,452,894 -2.20 0.9580
2023-02-14 2022-12-31 13F MERCK COM 58933Y105 13,390,230 -305,063 -2.23 1,485,633 25.94 1.0613
2023-01-13 2022-09-30 13F/A-1 MERCK COM 58933Y105 13,695,293 2,764,651 25.29 1,179,621 18.32 0.8838
2022-11-14 2022-09-30 13F MERCK COM 58933Y105 13,695,293 2,764,651 1,179,621 0.8831
2022-08-15 2022-06-30 13F MERCK COM 58933Y105 10,930,642 -1,027,093 -8.59 996,997 1.62 0.6875
2022-05-16 2022-03-31 13F MERCK COM 58933Y105 11,957,735 -638,043 -5.07 981,143 1.64 0.4737
2022-02-14 2021-12-31 13F MERCK COM 58933Y105 12,595,778 -4,881,403 -27.93 965,351 -26.46 0.4026
2021-11-16 2021-09-30 13F MERCK COM 58933Y105 17,477,181 -233,106 -1.32 1,312,697 -4.69 0.5741
2021-08-16 2021-06-30 13F MERCK COM 58933Y105 17,710,287 -5,758,495 -24.54 1,377,356 -23.87 0.5895
2021-05-17 2021-03-31 13F MERCK & CO. COM 58933Y105 23,468,782 -439,522 -1.84 1,809,218 -7.49 0.8260
2021-02-16 2020-12-31 13F MERCK & CO. COM 58933Y105 23,908,304 -3,832,056 -13.81 1,955,653 -15.01 0.9086
2020-11-16 2020-09-30 13F MERCK & CO. COM 58933Y105 27,740,360 -3,855,376 -12.20 2,300,923 -5.83 1.1996
2020-08-14 2020-06-30 13F MERCK & CO. COM 58933Y105 31,595,736 2,287,614 7.81 2,443,281 8.35 1.3715
2020-05-14 2020-03-31 13F MERCK & CO. COM 58933Y105 29,308,122 353,907 1.22 2,255,001 -14.37 1.5520
2020-02-18 2019-12-31 13F MERCK COM 58933Y105 28,954,215 4,108,756 16.54 2,633,372 25.91 1.3483
2019-11-14 2019-09-30 13F MERCK COM 58933Y105 24,845,459 5,510 0.02 2,091,487 0.42 1.1329
2019-07-31 2019-06-30 13F MERCK COM 58933Y105 24,839,949 1,790,405 7.77 2,082,840 8.65 1.1342
2019-04-30 2019-03-31 13F MERCK COM 58933Y105 23,049,544 1,747,557 8.20 1,917,013 17.77 1.0625
2019-02-06 2018-12-31 13F MERCK COM 58933Y105 21,301,987 782,438 3.81 1,627,727 11.82 1.0381
2018-11-09 2018-09-30 13F MERCK COM 58933Y105 20,519,549 8,032,634 64.33 1,455,653 92.05 0.7778
2018-08-10 2018-06-30 13F MERCK COM 58933Y105 12,486,915 3,682,328 41.82 757,959 58.04 0.4321
2018-05-14 2018-03-31 13F MERCK COM 58933Y105 8,804,587 -127,541 -1.43 479,589 -4.61 0.2826
2018-03-12 2017-12-31 13F/A-1 MERCK COM 58933Y105 8,932,128 2,226,564 33.20 502,760 17.10 0.3096
2018-02-09 2017-12-31 13F MERCK COM 58933Y105 8,932,128 2,226,564 502,760
2017-11-14 2017-09-30 13F MERCK COM 58933Y105 6,705,564 4,243,246 172.33 429,347 172.06 0.2752
2017-08-17 2017-06-30 13F/A-1 MERCK COM 58933Y105 2,462,318 2,058,407 509.62 157,812 514.96 0.1076
2017-08-14 2017-06-30 13F MERCK COM 58933Y105 2,462,318 2,058,407 157,812
2017-05-03 2017-03-31 13F MERCK COM 58933Y105 403,911 3,000 0.75 25,662 8.72 0.1802
2017-01-30 2016-12-31 13F MERCK COM 58933Y105 400,911 28,793 7.74 23,604 1.67 0.1741
2016-10-24 2016-09-30 13F MERCK COM 58933Y105 372,118 25,002 7.20 23,216 16.06 0.1711
2016-07-29 2016-06-30 13F MERCK COM 58933Y105 347,116 -29,194 -7.76 20,003 0.46 0.1663
2016-05-12 2016-03-31 13F MERCK & CO INC COM 58933Y105 376,310 18,215 5.09 19,912 5.28 0.1615
2016-02-03 2015-12-31 13F MERCK & CO INC COM 58933Y105 358,095 -6,994 -1.92 18,913 4.94 0.1518
2015-11-16 2015-09-30 13F MERCK & CO INC COM 58933Y105 365,089 -2,257 -0.61 18,023 -13.78 0.1588
2015-08-17 2015-06-30 13F MERCK & CO INC COM 58933Y105 367,346 -184,792 -33.47 20,904 -34.15 0.1643
2015-06-02 2015-03-31 13F/A-1 MERCK & CO INC COM 58933Y105 552,138 149,844 37.25 31,745 38.94 0.2449
2015-05-15 2015-03-31 13F MERCK & CO INC COM 58933Y105 552,138 31,745
2015-02-12 2014-12-31 13F MERCK & CO INC COM 58933Y105 402,294 -13,786 -3.31 22,848 -7.37 0.1647
2014-11-12 2014-09-30 13F MERCK & CO INC COM 58933Y105 416,080 -22,747 -5.18 24,667 -2.82 0.2320
2014-08-13 2014-06-30 13F MERCK & CO INC COM 58933Y105 438,827 332 0.08 25,384 1.92 0.2370
2014-05-08 2014-03-31 13F MERCK & CO INC COM 58933Y105 438,495 -768,435 -63.67 24,907 -58.78 0.2425
2014-01-14 2013-12-31 13F MERCK & CO INC COM 58933Y105 1,206,930 -8,532 -0.70 60,425 4.43 0.6105
2013-11-12 2013-09-30 13F MERCK & CO INC COM 58933Y105 1,215,462 -471,575 -27.95 57,862 -25.96 0.6383
2013-08-15 2013-06-30 13F MERCK & CO INC COM 58933Y105 1,687,037 1,687,037 78,152 0.9136
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.