S&P 500 Gains and Losses Today: Moderna Stock Pops as Execs Buy Shares, Express Cancer Vaccine Optimism

Major U.S. equities indexes fluctuated on Wednesday before gaining momentum in the afternoon to close the session higher.

Stocks came under pressure early in the day as an employment report showed a slower pace of private-sector hiring than expected, raising concerns about U.S. economic growth. However, equities markets reversed higher after President Donald Trump’s administration announced a one-month tariff reprieve for U.S. automakers.

The S&P 500 added 1.1% in the midweek session, changing course after tariff concerns contributed to losses in the first two trading days of March. The Dow also ended 1.1% higher, while the Nasdaq was up 1.5%.

Moderna (MRNA) shares popped 15.9%, notching Wednesday’s top performance in the S&P 500. The surge in the stock came after a top executive said the biotech firm anticipates a 2027 release of its personalized cancer vaccine, which it is developing in collaboration with Merck (MRK). In addition, reports that Moderna’s CEO purchased $5 million in common stock underlined internal confidence in the company’s upcoming performance.

Shares of military shipbuilder Huntington Ingalls Industries (HII) steamed 12.3% higher after Trump discussed investments in the shipbuilding industry in his address before a joint session of Congress on Tuesday evening. Shares of other defense contractors also posted gains following the president’s comments.

Celanese (CE) initiated cash tender offers aimed at purchasing it outstanding senior notes due in 2026 and 2027, and shares of the chemical and specialty materials company jumped 12.7%. Earlier this week, Celanese announced a collaboration with European building materials company Baumit to provide binders for sustainable paint and plaster solutions by applying carbon capture and utilization (CCU) technology.

Although CrowdStrike Holdings (CRWD) reported better-than-expected sales and profits for its fiscal fourth quarter, the cybersecurity company issued underwhelming full-year guidance, pointing to lingering pressure related to last summer’s global IT outage. CrowdStrike shares dropped 6.3%, suffering the steepest daily decline of any S&P 500 constituent. However, several analysts noted that the firm maintains a strong position in the cybersecurity space.

Crude oil futures prices moved lower following this week’s tariff developments and as the Organization of the Petroleum Exporting Countries (OPEC), along with several allied nations, confirmed plans to increase production levels starting in April. The price drop dragged down numerous oil and gas stocks. Shares of Marathon Petroleum (MPC) and Valero Energy (VLO) fell 5.3% and 4.6%, respectively.

Shares of medical device manufacturer ResMed (RMD) fell 3.3% after analysts at Stifel trimmed their price target on the stock. The analyst team noted that conversations with physicians raised concerns about the outlook for ResMed’s devices for treating sleep disorders, which could see an impact from the increasing prescription of GLP-1 weight-loss medications.