The AI boom has driven the 2026 stock market, but the S&P 500’s best performer so far this year is not a chipmaker. It is a COVID vaccine maker, up 663% after closing at $225 on Friday.

That lead rests on a cancer vaccine trial whose detailed results have not been released. In mid-August, the company’s shares were still down nearly 90% from their pandemic peak.

How Moderna Stock Climbed Past Every AI Name

The company is Moderna (MRNA), best known for its COVID shot. On August 19, it and drugmaker Merck said their experimental cancer vaccine had passed a final-stage trial in skin cancer patients.

The news landed after a rough stretch. COVID vaccine sales had collapsed, and Moderna cut more than 800 jobs last year.

Shares closed up 177% that day, then fell 24% the next, according to the Inquirer. BeInCrypto had already flagged Moderna’s 2026 comeback in June, when the stock was up 125% on a flu vaccine approval.

On Friday, the gains extended, with Moderna rejoining the Nasdaq-100, an index of Nasdaq’s largest non-financial companies.

More than 200 funds holding over $800 billion track it, Nasdaq said, so they had to buy the shares.

The same day, The New York Times reported a COVID-style national cancer vaccine push, expected to launch in December. Moderna closed 14% higher.

Moderna Stock Performance. Source: Yahoo Finance

AI names sit just behind. SanDisk, which sells memory chips to AI data centers, is up 566% this year, riding AI memory chip demand. The S&P 500 has gained about 14%.

October Is Critical For Moderna Stock Price

So far, Moderna and Merck have said the vaccine worked but have not shown how well. Investors get the full numbers on October 24, at a major cancer conference in Madrid.

“It provides proof of principle that personalised cancer vaccines work,” Marco Gerlinger, a professor at Barts Cancer Institute, told the Pharmaceutical Journal.

Notably, not every investor is buying the rally. Martin Shkreli, a former drug company executive, gives the Moderna stock bubble up to six months to burst.

Moderna is now worth about $89.8 billion, and rivals BioNTech and Genentech are testing a cancer vaccine of their own.

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