Key Highlights

● Illumina plunged on Friday, October 30, 2026, as health care otherwise rallied.

● Third-quarter Revenue of $1.13 billion missed consensus by about $20 million.

● Tariff refunds of $37 million passed to customers reduced reported revenue.

● Adjusted Earnings of $1.44 a share beat the $1.36 estimate.

Illumina (NASDAQ:ILMN) plunged on Friday, October 30, 2026, after the gene-sequencing company reported third-quarter revenue that missed Wall Street's expectations. The shares fell steeply in morning trading and remained sharply lower through the session; reports differed on the size of the move.

The decline stood out because health care was otherwise one of the market's strongest sectors on the day, hitting a record high as investors rotated out of technology. The Nasdaq Composite fell 747.73 points to 25,437.00, its worst day since June 5.

The revenue shortfall

Illumina reported third-quarter revenue of $1.13 billion, about $20 million below consensus. That figure reflected $37 million of Tariff refunds that the San Diego-based company passed back to customers. Excluding those refunds, revenue would have been $1.17 billion.

Other parts of the report were stronger. Adjusted earnings came in at $1.44 a share against a $1.36 estimate, according to market data; another source cited a different adjusted figure of $1.62, a discrepancy that was not resolved. The company also raised its full-year revenue guidance to $4.64 billion to $4.66 billion.

CEO Jacob Thaysen credited "healthy clinical Demand and robust NovaSeq X placements" for the company's performance. NovaSeq X is Illumina's flagship high-throughput sequencing system, used by labs to read DNA at scale.

Still, the headline revenue miss drew the market's focus, and the stock fell sharply despite the earnings beat and the higher outlook.

A day of divergence in health care

Illumina's slide came as many other health care stocks surged. Regeneron (NASDAQ:REGN) was the S&P 500's top gainer after third-quarter revenue of $5.12 billion beat the $4.54 billion estimate. Gilead Sciences (NASDAQ:GILD) and DexCom rose after their results, and AbbVie (NYSE:ABBV), Johnson & Johnson (NYSE:JNJ), Pfizer (NYSE:PFE), Eli Lilly (NYSE:LLY) and Cardinal Health reached 52-week highs.

Illumina was not the only health care laggard. Stryker (NYSE:SYK) fell after third-quarter revenue of $6.52 billion missed the $6.61 billion estimate and the company cut its full-year organic growth guidance. Canaccord downgraded Stryker to Hold from Buy.

The broader selloff

The market as a whole had a rough day. Intel (NASDAQ:INTC)'s weak fourth-quarter outlook and warning of cash burn sent its shares to a record one-day decline and dragged the Philadelphia Semiconductor index down to 10,688.80. Amazon (NASDAQ:AMZN) reported trailing 12-month free Cash Flow of negative $42.4 billion as spending on AI infrastructure ballooned, and Alphabet (NASDAQ:GOOGL) was still under pressure after its worst day ever on Thursday.

The S&P 500 fell 140.32 points to 7,580.07, the Dow Jones Industrial Average lost 572.25 points to 51,770.31, and the Russell 2000 slid 47.37 points to 2,811.84. Oil stayed above $100, with December WTI crude settling at $104.12, and a reported $6.3 billion hack at crypto exchange Binance hit digital-asset stocks.

"The earnings bar is very high," said an Investment strategist, speaking about the market more broadly.

What to watch

Investors will look for more detail on the tariff refunds and whether they recur, since they weighed on reported revenue. Placements of NovaSeq X systems and clinical demand, both highlighted by management, will be key indicators of Illumina's growth.

The raised full-year revenue guidance of $4.64 billion to $4.66 billion sets a target for the fourth quarter. More broadly, health care earnings continue next week with Pfizer on Tuesday, November 3, the same day as the midterm elections, and the October jobs report arrives on Friday, November 6.