Moderna Stock Skyrockets Over 100%

August 19, 2026 1:18 PM ET Shares of Moderna more than doubled Wednesday after the company and Merck announced positive results from a late-stage trial of an experimental cancer vaccine, though the companies have yet to release detailed data from the results.The Phase 3 trial met its primary endpoint, according to the drugmakers, with the vaccine combination significantly improving the amount of time patients remained free of melanoma compared with Keytruda alone. But Moderna and Merck have not yet disclosed the specific effect size, survival times or full statistical results for the trial, leaving investors and outside researchers waiting for a clearer picture of how substantial the benefit actually was. The trial tested Moderna’s mRNA-based vaccine alongside Merck’s Keytruda immunotherap