Merck and Moderna say cancer vaccine shows signs of preventing recurrence of melanoma​Merck and Moderna say cancer vaccine shows signs of preventing recurrence of melanoma 

 Pharmaceutical giants Moderna and Merck said that an experimental vaccine treatment has shown signs of preventing cancer from returning or spreading in a study of high-risk melanoma patients. NBC News health reporter Aria Bendix explains what happens next.  ​​Pharmaceutical giants Moderna and Merck said that an experimental vaccine treatment has shown signs of preventing cancer from returning or spreading in a study of high-risk melanoma patients. NBC News health reporter Aria Bendix explains what happens next.