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.
Source: [NBC News](https://www.nbcnews.com/now/video/merck-and-moderna-say-cancer-vaccine-shows-signs-of-preventing-recurrence-of-melanoma-268536389991)