S&P 500 closes 0.21% higher as Moderna's 176.97% melanoma result pays for a chip equipment selloff

S&P 500 close: 7,707.98 (+0.21%) Equal weight vs cap weight: RSP.US +1.04% against SPY.US +0.21% Sentiment: mixed

The S&P 500 closed at 7,707.98 on 19 August 2026, up 0.21%, with a 3.51% health care rally covering a 1.07% fall in technology. Moderna MRNA.US finished +176.97% at $174.38, roughly doubling again from the 91.10% pre-market gain, after the Phase 3 INTerpath-001 trial of intismeran autogene plus Keytruda met its recurrence-free and distant-metastasis-free survival endpoints in resected stage IIB-IV melanoma, carrying partner Merck MRK.US +12.60%. The US Treasury said it will lift individual longer-dated buyback operations from $2 billion to a minimum of $4 billion from 9 September, which pushed the 10-year yield 6 basis points down to 4.65% and the dollar index 0.86% lower to 98.80.

What moved the index

The S&P 500 added 16.22 points to 7,707.98 on 19 August 2026, a 21 basis point move assembled from sector contributions running between +42 and -40 basis points.

• Health care (XLV +3.51%) contributed about +42 basis points at roughly 12% index weight. The Moderna and Merck readout lifted the whole sector: IBB +6.58%, XBI +5.90%, LLY.US +4.46%.
• Technology (XLK -1.07%) subtracted about -40 basis points at roughly 37% weight. Semiconductor test equipment led the selling, with AEHR.US -12.41% off a 510% year-to-date gain through Tuesday, TER.US -6.09% and FORM.US -7.55%. SOXX closed -2.21%, AVGO.US -4.57%, INTC.US -4.02%, AMD.US -3.71%.
• Consumer discretionary (XLY +1.92%) added about +19 basis points at roughly 10% weight. TSLA.US +4.23% and AMZN.US +2.46% did most of it, with TGT.US +4.28% on second quarter results.
• Financials (XLF -0.62%) cost about -8 basis points at roughly 13% weight as the Treasury buyback expansion dragged the 10-year to 4.65% and the 30-year 9 basis points to 5.19%.

Those four drivers net to roughly +13 basis points. The remaining seven sectors add about +9, for +22 against the 21 basis points the index moved.

Session highlights

• RSP.US +1.04% against SPY.US +0.21% put the equal weight S&P 500 ahead of the cap weighted index by 83 basis points. The average S&P 500 stock rose five times as far as the cap weighted benchmark.
• MRNA.US +176.97% handed short sellers a reported $5 billion loss, their worst single day in the stock, on the first positive Phase 3 readout for an individualized mRNA cancer therapy.
• GDX +9.42% and SIL +9.53% led the miners as GLD closed +3.84% and SLV +4.47%. NEM.US rose 7.85% and AEM.US 11.12%.
• EL.US +16.30% to $98.01 after fourth quarter results beat and FY27 sales guidance came in above estimates at the midpoint.
• VIX fell 6.00% to 14.89 while single stock moves ran from +176.97% to -12.41% inside the index.
• MRVL.US closed +9.85% after Tuesday night's filing on an expanded Google custom silicon deal, holding most of the 11.94% pre-market gain.

Sector scorecard

• Best: Health care (XLV) +3.51%
• Worst: Technology (XLK) -1.07%
• Dispersion (best minus worst): 4.58 points
• Six sectors rose, four fell and utilities (XLU) closed unchanged. Health care held the widest internal spread: IBB rose 6.58% and XBI 5.90% while UNH.US fell 1.35%.

Top movers

After-hours earnings

Wolfspeed WOLF.US reported fiscal fourth quarter results after the 4:00pm ET close on 19 August 2026 and traded about 8% lower after the bell on Yahoo Finance's earnings coverage. Adjusted loss per share of $2.26 missed a $1.47 estimate and revenue of $149.6 million came in under a $150 million consensus. The stock had already closed the regular session 7.53% lower at $29.09 alongside the rest of the chip group, so the after hours print deepens a fall already underway. Options had priced a 14% move into the print, and management hosted the call at 5:00pm ET.

Notable announcements

• US Treasury will raise individual longer-dated buyback operations from $2 billion to a minimum of $4 billion from 9 September. That single line moved the 10-year 6 basis points to 4.65%, the 30-year 9 basis points to 5.19%, and the dollar index 0.86% to 98.80.
• FOMC minutes for the 28 to 29 July meeting, released 2:00pm ET, recorded a 9 to 3 vote to hold. Hammack, Kashkari and Logan each preferred a quarter point increase, and participants noted that policy tightening would likely be necessary if inflation did not decline.
• LOW.US +2.02% on adjusted EPS of $4.40 against a $4.22 estimate, with net sales of $25.96 billion short of the $26.16 billion consensus.
• TJX.US -4.21% despite raising full year profit guidance, after third quarter adjusted EPS guidance of $1.30 to $1.32 landed under the $1.35 consensus.
• FN.US -5.81%, a second session lower after Tuesday's 19.38% fall on the off balance sheet AI commitment analysis.

Next session catalysts (ET)

• Thu 07:00 Walmart WMT.US second quarter results, call at 8:00am ET. Consensus sits at $0.74 EPS on $186.8 billion of revenue.
• Thu 08:30 Weekly initial jobless claims.
• Thu 08:30 Philadelphia Fed manufacturing survey for August.
• Thu 27 to Sat 29 Aug Jackson Hole symposium on "Financial Innovation: Implications for Payments and Policy", with Fed chair Kevin Warsh delivering his first keynote on Friday 28 August.

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