Cancer Vaccine Shows Sharp Drop in Melanoma Deaths

Patients treated with a personalized mRNA vaccine alongside standard therapy faced a 42 percent lower risk of death or melanoma recurrence compared with those receiving standard treatment alone. That is the central finding from a late-stage trial of a vaccine candidate developed by Merck and Moderna for melanoma, the most lethal form of skin cancer. The companies announced the results Thursday, October 22, 2026.

The study enrolled 1,137 patients whose stage IIB through IV melanoma had already been surgically removed before they entered the trial. Participants were assigned two to one to receive either the personalized vaccine combined with standard treatment or standard treatment by itself. The standard treatment used in both groups was Merck's monoclonal antibody drug Keytruda.

The vaccine is designed for each patient's own tumor profile, a concept that has been central to the companies' approach from the start. Moderna CEO Stéphane Bancel said in a statement, "From the beginning, we believed mRNA technology could make it possible to develop cancer treatments uniquely matched to each patient's tumor." He added that the trial results "mark a defining moment for that vision and show what's possible when we rethink how medicines are made."

The trial results also "reinforce our conviction that mRNA has the potential to fundamentally change how we treat cancer," Bancel said in the same statement. The companies have said they are in discussions with regulators about seeking approval for the vaccine, and the full data set has been accepted for publication in the New England Journal of Medicine.

The results were first reported in August, when the partners said the trial had met its goal but withheld detailed figures until a scientific meeting. That meeting, the European Society of Medical Oncology conference in Madrid, Spain, is underway this week. The data was slated for presentation Saturday, but an oncology news site reported the figures ahead of schedule, prompting the companies to release the top-line results early.

The 42 percent figure reflects a comparison of death or recurrence outcomes between the two groups in the trial, as reported by the companies. The trial's design, with two patients assigned to the vaccine combination for every one assigned to standard treatment alone, was set up to evaluate that comparison.

The companies are moving to engage with regulatory authorities on approval, and the full data has been accepted for publication in the New England Journal of Medicine. The results add to broader interest in mRNA technology and individualized cancer-targeting medicines as a potential new direction for treatment.

Open questions remain around the details of the trial, including how the results break down across patient subgroups and what other data the full publication will include. The conference presentation in Madrid is scheduled for Saturday, October 24, 2026, and the full paper in the New England Journal of Medicine is expected to provide further information.

For patients who have had melanoma surgically removed, the trial's findings address the risk that the disease returns or leads to death. The vaccine is given alongside Keytruda, which is already in use, rather than replacing it. The companies have not announced a timeline for any regulatory filing or approval decision.