TLDR
- Moderna stock jumped 177% on Wednesday after positive Phase III trial results for its melanoma cancer vaccine, intismeran.
- The move makes it only the second S&P 500 stock to more than double in a single day in 25 years.
- MRNA is now up 491% year-to-date, second only to Sandisk among S&P 500 performers.
- Analysts raised price targets and upgraded coverage but cautioned the good news may already be priced in.
- The stock pulled back after the initial surge as investors weighed valuation concerns.
Moderna stock hit 177% on Wednesday following Phase III trial results for intismeran, its personalized melanoma vaccine developed alongside Merck’s Keytruda. The stock opened at a jaw-dropping gain before pulling back as investors began digesting what the move actually means.
The rally pushed MRNA’s year-to-date gain to 491%, making it the second-best performing S&P 500 stock in 2026. Only memory-storage company Sandisk has done better. Dell, Micron, and Seagate round out the top five.
It is only the second time in 25 years that an S&P 500 stock has more than doubled in a single session. The last time it happened was Hartford Insurance Group back in December 2008.
Before the trial data dropped, Moderna had already climbed 114% in 2026. Investors had been pricing in hopes that the cancer vaccine would work. The data still caught Wall Street off guard.
Analyst Reaction
Analysts moved quickly after the results. Price targets were raised across the board and several firms upgraded their coverage, calling the melanoma data a watershed moment for Moderna’s oncology pipeline.
But the tone stayed cautious. The core concern is that the good news may already be priced into the stock after such a massive one-day move. Several analysts flagged valuation and risk-reward as reasons to hold off chasing the rally.
The stock slipped after the initial surge, a pattern that often follows headline-driven spikes when institutional investors use strength to trim positions.
Moderna is still burning cash. COVID-19 revenue continues to fade, and newer products are ramping slowly. A delay to its norovirus vaccine program earlier this year showed how timing risks can weigh on results.
Pipeline and Risk
Beyond melanoma, Moderna has a broad mRNA pipeline and a growing respiratory vaccine portfolio. The company has multiple programs in development, which reduces its reliance on any single product.
Its balance sheet remains solid, which gives it runway to push those programs forward without immediately needing to raise capital.
That said, if product launches slip or uptake disappoints, the pressure on earnings could mount. Trial timelines are notoriously hard to predict, and Moderna has already seen that play out with the norovirus delay.
Anyone who bought MRNA following the hantavirus outbreak speculation in May is sitting on extraordinary gains. The stock had risen 114% even before Wednesday’s move.
Moderna’s current market cap sits at $25.14 billion. Average daily trading volume runs around 10 million shares, a number that was almost certainly blown past on Wednesday.
The iShares Biotechnology ETF is up 56% over the past year, a sign that the broader biotech sector has been recovering even as vaccine makers faced headwinds from the political environment following RFK Jr.’s appointment as health secretary in late 2024.
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