This market will resolve to "Yes" if it is officially announced that Merck & Co. (MRK) will be, has been, or is being acquired by or merged with Moderna (MRNA), or vice versa, by December 31, 2026, 11:59 PM ET. Otherwise, this market will resolve to "No". A qualifying merger or acquisition must encompass both MRK and MRNA or their subsidiaries. An announcement by MRK or MRNA within this market's timeframe will qualify for a "Yes" resolution, regardless of whether or when the announced acquisition/merger actually occurs. A bid or offer announcement without the indication of a settled agreement will not qualify. Announcements of partial sales may count, as long as the acquiring company announces the acquisition of a controlling interest in the other company. A "controlling interest" refers to a change in ownership sufficient to control the company's strategic decisions (typically more than 50% of equity, or equivalent control via voting and governance rights). Transactions or investments that do not result in a transfer of controlling interest will not count. The primary resolution source for this market will be official information from MRK and MRNA; however, a consensus of credible reporting may also be used.