Here’s what Moderna’s latest mRNA cancer vaccine data actually showNEWS | 23 October 2026I agree my information will be processed in accordance with the Scientific American Inc. Privacy Policy . We leverage third party services to both verify and deliver email. By providing your email address, you also consent to having the email address shared with third parties for those purposes.
Data from Moderna and Merck’s phase 3 clinical trial for an mRNA-based skin cancer vaccine leaked on social media on Thursday, prompting the pharmaceutical companies to release an early look at the results of the trial.
The results, which triggered Moderna’s stock to drop, are “really encouraging,” says Karen Knudsen, CEO of the Parker Institute for Cancer Immunotherapy, a nonprofit. This kind of mRNA cancer vaccine was “fiction” 10 years ago, she says. “It was thought to be very difficult to do.”
As Scientific American previously reported, the Moderna-Merck clinical trial includes two treatments: a personalized mRNA-vaccine called intismeran autogene, which works by instructing the body in how to identify and fight cancer, and pembrolizumab (sold as Keytruda), a drug designed to prevent cancer from “hiding” from our immune system, according to Merck.
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The clinical trial included 1,137 cancer patients with “high risk” melanoma, a type of skin cancer. Together, the mRNA vaccine and pembrolizumab reduced the risk of cancer recurrence or death by 42 percent in people, after a median period of about two years, compared to people on pembrolizumab alone. On top of that, the dual treatment reduced the risk of cancer spreading to other parts of the body or death by 38 percent over just pembrolizumab, according to Moderna and Merck.
The findings don’t yet include overall survival, Knudsen notes. “Did people who got the vaccine live longer than people who didn't? And what was their quality of life?” she asks. Those results are coming. But the new findings are “really, really good milestones along the way,” she says.
“From the beginning, we believed mRNA technology could make it possible to develop cancer treatments uniquely matched to each patient’s tumor, Moderna CEO Stéphane Bancel said in a statement. “These results reinforce our conviction that mRNA has the potential to fundamentally change how we treat cancer.”
The results have been accepted for publication in the New England Journal of Medicine, Merck and Moderna said. Now, the companies are “engaging with regulatory authorities” to seek approval for their mRNA vaccine.
Moderna and Merck did not immediately reply to requests for comment from Scientific American.Author: Claire Cameron. Jackie Flynn Mogensen. Source
