Moderna and Merck Shares Decline Following Reports of Potential Data Leak for Melanoma Vaccine

On October 22, 2026, shares of Merck & Co., Inc. and Moderna declined due to reports of a potential data leak concerning their experimental melanoma vaccine. The companies are set to present full Phase 3 trial data at a medical conference in Madrid, where the study is expected to confirm its primary and secondary endpoints. The market's reaction to the leak occurred prior to the formal data presentation.