Swingfolio Daily — US Markets
US briefings — Wednesday, August 19, 2026
Pre-market setup and closing-bell recap for Wednesday, August 19, 2026. Observations only — no trade advice.
Wednesday, August 19, 2026
S&P 500 futures flat as a Phase 3 vaccine result offsets a 5.80% Kospi fall
S&P 500 futures sat at 7,716.50, up 0.03%, at 08:40 ET on 19 August 2026. Moderna MRNA.US traded 91.10% higher and Merck MRK.US 7.20% higher pre-market after their individualized melanoma vaccine met both endpoints in the Phase 3 INTerpath-001 trial. Marvell MRVL.US rose 11.94% after an SEC filing disclosed an expanded Google custom silicon partnership and a warrant over 58.97 million shares. The Kospi fell 5.80% to 6,471.17 on a Korea Exchange sidecar and the 30-year Treasury yield eased to 5.27%.
S&P 500 closes 0.21% higher as Moderna's 176.97% melanoma result pays for a chip equipment selloff
The S&P 500 closed at 7,707.98 on 19 August 2026, up 0.21%, as health care added about 42 basis points and technology cost about 40. Moderna MRNA.US finished +176.97% at $174.38 after the Phase 3 INTerpath-001 trial of intismeran autogene plus Keytruda met both endpoints in resected melanoma, carrying Merck MRK.US +12.60%. A US Treasury plan to double longer-dated bond buybacks from 9 September cut the 10-year yield to 4.65% and the dollar index 0.86%, lifting GDX 9.42%. Semiconductor test equipment fell hardest, with AEHR.US -12.41%.