Merck and Moderna’s melanoma vaccine shows positive Phase 3 results, boosting investor confidence

Merck and Moderna announced that their personalized melanoma vaccine met the primary endpoint of recurrence‑free survival in a Phase 3 trial when given together with Keytruda. The study showed patients lived longer without cancer returning compared with Keytruda alone.

Following the news, Merck’s stock rose about 12% to $152.20, while Moderna’s shares jumped roughly 176% to $174.38, reflecting strong market enthusiasm for the data.

Analysts said the result gives Merck a clear growth path even as Keytruda faces upcoming loss of exclusivity, improving sentiment around the company’s future.

Investors had previously been skeptical about the vaccine’s chances, but the trial outcome shifted expectations and highlighted the potential of mRNA‑based cancer vaccines.