Moderna falls 18% as strong cancer-vaccine data misses sky-high hopes

What happened

• Moderna and Merck are testing a personalized melanoma vaccine, built from each patient’s own tumor and given with Merck’s Keytruda. The late-stage trial enrolled 1,137 patients.
• In August the companies said the trial worked but gave no numbers. The full presentation is Saturday, Oct 24, at ESMO in Madrid.
• Around 12:30 p.m. ET on Thursday, Oct 22, a medical news site posted the results early, then took the post down. Merck and Moderna released them officially at 2:59 p.m.
• Moderna fell as much as 26%, its worst intraday drop on record, from $245.81 to $180.80. It closed at $202.63, down 17.6%, erasing about $17 billion in market value (more than $20 billion at the low).
• Merck closed down about 2%. The S&P 500 fell 1.2% and the Nasdaq 2.6%, but biotech stocks were only modestly lower.

What the results showed

Compared with Keytruda alone, adding the vaccine showed:

• 42% lower risk of the cancer returning or death (the main goal); 58% after the six-month vaccine course, the companies report
• 82% vs. 70% alive and cancer-free at 2 years
• 38% lower risk of distant spread or death
• No new safety problems
• Overall survival: data not yet mature, with an early favorable trend, the companies report

By normal standards this is a success, likely the first personalized cancer vaccine to win a large, late-stage trial. RBC said the result was at the low end of expectations, BioSpace reported.

Why the market reacted this way: expectations vs. reality

Investors hoped for more

• An earlier, smaller trial cut the risk by 49%, and many investors hoped for a repeat. (The big trial included some earlier-stage patients, whose cancer returns less often, so experts expected a somewhat smaller benefit.)
• Citi had called a risk cut of about 35% a clear win, and UBS said that was roughly what the market expected. The result beat that bar; the share price assumed much more.

The price had run far ahead

• Moderna started 2026 at about $30. It nearly tripled in one day (up 177%) on the August “it worked” news, then kept climbing on a reported government cancer-vaccine program and its addition to the Nasdaq-100, reaching about $246 on Oct 21, roughly 8 times its January price.
• Moderna still loses money (about $8 per share expected this year), and COVID vaccine sales keep shrinking.
• In September Citi told clients to sell, saying a ~$200 share price implied about $26 billion a year in cancer sales (about $13 billion of it Moderna’s), nearly 7 times Citi’s own forecast. Other analysts see peak sales for this vaccine of about $3 billion a year, shared with Merck. The average analyst price target is around $100 (MarketBeat).

Traders took profits

• UBS and William Blair analysts called it a classic “sell the news” reaction to the run-up. The leak, the deleted post and the hurried official release added to the nervous selling.

Does this change Moderna’s future?

What did NOT change

• The vaccine remains on track for an approval filing and is in 9 mid- and late-stage trials, including lung, bladder and kidney cancer. Lung cancer is a much bigger market than melanoma.

What DID change

• The best case got a little smaller: 42% instead of 49% points to a somewhat smaller benefit and perhaps lower sales. Even after the drop, the stock is almost 7 times its January price and above most analyst targets.

Our read

This is a reset in expectations, not a sign the company is broken. The $246 price assumed everything would go perfectly.