Moderna and Merck said their personalized mRNA cancer vaccine, used together with the immunotherapy drug Keytruda, reduced the risk of melanoma returning or causing death by 44% compared with Keytruda alone in a phase 3 study. The companies said the result was based on three years of follow-up in a large trial.

The finding adds momentum to a new generation of cancer treatments designed to train the immune system to recognize tumor-specific markers. Unlike traditional vaccines, the mRNA approach is customized for each patient, aiming to help the body target cancer cells more precisely after surgery and other standard care.

While the latest data is encouraging, the treatment still needs to clear further regulatory and clinical hurdles before it can become widely available. Researchers and doctors will likely look closely at longer-term safety, durability of benefit, and whether the results hold up across broader patient groups.

If confirmed, the study could mark an important step forward in personalized cancer therapy and offer new hope for patients facing high-risk melanoma.