Cancer vaccine reduces melanoma risk 49% after five years

New data out of New York University’s Perlmutter Cancer Center suggests a precision-made mRNA vaccine paired with established immunotherapy can dramatically lower melanoma’s return rate years after surgery. Presented at the American Society of Clinical Oncology’s 2026 meeting and published in the Journal of Clinical Oncology, the findings offer fresh evidence that personalized cancer vaccines may change the long-term outlook for patients who have had tumors removed.

Researchers tested the vaccine intismeran alongside pembrolizumab (Keytruda) and followed patients for five years. The combination produced substantially better outcomes than immunotherapy alone, with improvements in recurrence, distant spread, and overall survival that could shift how clinicians approach post-surgical melanoma care.

Five-year follow-up shows a 49% cut in recurrence or death

After a half-decade of monitoring, patients who received the intismeran vaccine plus pembrolizumab were notably more likely to remain cancer-free than those treated with pembrolizumab alone. In the trial:

• 68.8 percent of patients in the vaccine-plus-immunotherapy arm remained without recurrence at five years.
• By comparison, 49.1 percent of patients who received only pembrolizumab were recurrence-free.
• That difference equates to a 49 percent reduction in the risk of recurrence or death for the combination therapy group.
• The combination also lowered the risk of distant metastasis by 59 percent.
• Overall survival was higher in the combination arm: 92.2 percent versus 71.3 percent in the immunotherapy-only group.

These outcomes come from the phase 2b KEYNOTE-942 study and represent clinically meaningful gains for people treated after surgical removal of melanoma tumors.

What intismeran is and how a personalized mRNA vaccine trains the immune system

Intismeran is an mRNA vaccine engineered to teach the immune system to spot and eliminate melanoma cells. Unlike one-size-fits-all approaches, this vaccine is customized for each patient based on the unique fingerprint of their tumor.

How personalization works

• Scientists sequence the tumor to identify abnormal proteins—called neoantigens—produced only by the cancer.
• Up to 34 patient-specific neoantigens were selected to design each vaccine.
• The mRNA instructs immune cells to make short pieces of those proteins, prompting T cells to recognize and attack any remaining cancer cells carrying the same targets.

By priming T cells against tumor-specific neoantigens, the vaccine aims to reduce the chance that microscopic disease left after surgery will regrow or spread.

Trial design, patient group and safety profile

The KEYNOTE-942 trial enrolled patients at cancer centers in the United States and Australia between 2019 and 2021. Participants had undergone surgery to remove melanoma and were then randomized to receive pembrolizumab with or without the personalized vaccine.

• Study arms: 107 patients received the vaccine plus pembrolizumab; 50 patients received pembrolizumab alone.
• Follow-up length: five years after treatment.
• Deaths during follow-up: seven in each treatment arm, most attributable to cancer.

Side effects were described as manageable. Common adverse reactions included:

• fatigue
• pain at the injection site
• chills

Why combining vaccines with checkpoint inhibitors can be powerful

Checkpoint inhibitors like pembrolizumab block molecules (for example, PD-1) that tumors exploit to hide from the immune system. However, some melanomas are adept at dodging these drugs. Adding a personalized vaccine can broaden and sharpen the immune attack by specifically expanding T cells that recognize tumor neoantigens.

Researchers say this dual approach can both reveal cancer cells to the immune system and arm T cells with the precise targets needed to hunt down residual disease. NYU’s team notes the results raise hope that similar mRNA vaccine–plus–immunotherapy strategies could work for other high-mutation cancers that have been tough to control.

Ongoing research, where intismeran could go next

A multicenter phase 3 trial is already underway to test intismeran as first-line therapy in combination with pembrolizumab for melanoma. The vaccine is also being evaluated in trials aimed at preventing recurrence in lung and other cancers.

Additional trial and real-world data will be key to determining:

• whether the five-year benefits are replicated in larger, more diverse populations;
• how long vaccine-induced protection lasts;
• which tumor types and mutation profiles respond best to this approach.

Context: melanoma trends and industry support

Skin cancer remains the most diagnosed cancer in the U.S., with projected new cases in 2026 reaching roughly 112,000. Advances in targeted therapies and immunotherapy have driven a decline in melanoma deaths over the past decade, and personalized vaccine strategies could accelerate that progress.

The KEYNOTE-942 study received financial support from Moderna, which makes intismeran, and from Merck, the manufacturer of pembrolizumab.

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Michael Thompson

Michael Thompson is an experienced journalist covering U.S. and global news. With ten years on the front lines, he breaks down political and economic stories that matter. His precise writing and keen attention to detail help you grasp the real‑world impact of every event.