This study checks if a new cancer vaccine called **mRNA-4157**, combined with a drug named **pembrolizumab**, helps stop melanoma (a type of skin cancer) from coming back after surgery. **Melanoma** is a dangerous skin cancer. **Pembrolizumab** is a medicine that helps your immune system fight cancer. **Adjuvant therapy** is extra treatment given after surgery to kill any remaining cancer cells. To join, you must have had melanoma removed from your skin that spread to a lymph node, and be at high risk for it coming back. You can't have any other active cancers or certain health conditions like infections or heart problems.
Key Points:
- Study lasts for about a year with regular visits.
- Participants receive the vaccine and pembrolizumab, or pembrolizumab alone.
- Includes health checks and blood tests. Possible side effects from treatment.