Moderna short-sellers stare at record one-day loss as shares surge on vaccine data

Moderna

19/08/2026 15:39

Aug 19 (Reuters) - Investors betting against shares of Moderna MRNA.O faced record one-day losses on Wednesday as the biotech company's stock more than doubled in value following upbeat data on its personalized mRNA cancer therapy.
At $159, short sellers were on pace for about $4.8 billion in mark-to-market losses, according to data analytics firm ORTEX. 
"With each shorted share now down almost $100, that is exactly the kind of pressure that can trigger a squeeze," said Peter Hillerberg, co-founder of ORTEX. 
"There is clearly a real catalyst behind a move this size, but with a short base this large, shorts scrambling to cover are adding fuel and can keep driving the price higher." 
The company's shares rallied to hit $163 before pulling back slightly to trade at $148.3. 
Short interest in Moderna's shares stood at 13.5% of its free-float as of Wednesday, making it one of the most-shorted large-cap stocks, ORTEX estimates. 
Moderna shares were set for a record one-day percentage gain after its personalized mRNA cancer therapy, developed with Merck MRK.N, reduced the risk of skin cancer recurrence and spread in a late-stage trial when combined with Keytruda. 


     

 (Reporting by Shashwat Chauhan in Bengaluru; Editing by Sriraj Kalluvila)
 ((Shashwat.Chauhan@thomsonreuters.com;))