**Cancer Vaccines: Personalized Medicine's Next Breakthrough** Cancer vaccines represent one of oncology's most ambitious frontiers: treatments custom-built from a patient's own tumor mutations to train the immune system to recognize and destroy lingering cancer cells. The flagship effort—Moderna and Merck's personalized mRNA vaccine (mRNA-4157/V940, also called intismeran), paired with Merck's blockbuster immunotherapy Keytruda—has moved from bold concept to clinical reality. The momentum turned tangible in 2026. Detailed late-stage melanoma data, unveiled amid an embargo hiccup at the ESMO conference, confirmed the vaccine met key endpoints—slashing melanoma recurrence risk by 42% versus standard treatment. Yet executives Moderna's Stephen Hoge and Merck's Dean Li struck a measured tone at the STAT Summit, acknowledging a "lot of exploring to do" as they map next steps. The implications ripple widely. Validating personalized mRNA oncology could unlock pipelines across pancreatic, lung, and colorectal cancers—Tango's 82% response rate in pancreatic cancer hints at the breadth ahead. Investors and patients alike should watch regulatory filings, expanded tumor trials, and manufacturing scale-up. After decades of promise, therapeutic cancer vaccines finally appear to be delivering.