Short Sellers Just Lost $5B on the Wrong Pharma Bet: Cancer Vaccine Sends Stock Soaring 177%

Investors are reassessing Moderna after its cancer vaccine achieved key Phase 3 goals, offering a potential new source of growth. (Credit: Fletcher, CC BY 4.0/Wikimedia Commons)

For years, Moderna's critics had made the same bet. The company had become synonymous with its COVID-19 vaccine. But demand for that product fell as the pandemic receded. Its shares then suffered four straight years of losses and fell sharply from their 2021 peak. Short sellers believed the decline would continue. On Wednesday, that bet went badly wrong.

Moderna shares closed 177% higher after the company and Merck announced promising results from a late-stage trial of their experimental personalised cancer vaccine. The move dealt an estimated $5 billion blow to short sellers, according to S3 Partners data reported by Bloomberg. The surge was Moderna's largest-ever percentage gain and offered investors a new reason to look beyond the company's fading COVID-19 vaccine business.