Moderna Shares Fall 25% After Unplanned Early Release of Cancer Vaccine Data

Moderna shares fell more than 25%, and Merck shares fell more than 3%, on October 22, 2026, after apparent early release of results for a cancer vaccine tailored to each patient, Investing.com reported. The companies did not schedule the release. Moderna's August melanoma (skin cancer) trial result was based on an early, incomplete look at the data.