HealthMerck and Moderna report that a personalized mRNA vaccine helped prevent skin cancer from returning in high-risk patients. Observers greeted the news with enthusiasm but noted that full data from the ongoing late-stage study has yet to be released.Experimental treatment combines a tailored vaccine with immunotherapy; companies say it met key trial targetsJulie Steenhuysen · Thomson Reuters · Posted: Aug 19, 2026 11:31 AM EDT | Last Updated: 1 hour agoListen to this articleEstimated 4 minutesThe audio version of this article is generated by AI-based technology. Mispronunciations can occur. We are working with our partners to continually review and improve the results.Sunbathers bask at Toronto's Woodbine Beach last year. Melanoma Canada says melanoma is one of the most common types of cancer found among Canadians aged 15 to 29 and 30 to 49. (Evan Mitsui/CBC)Merck and Moderna said on Wednesday a study of a personalized mRNA vaccine combined with the immunotherapy drug ‌Keytruda reduced skin cancer recurrence and spread compared with Keytruda alone, the first positive late-stage trial results for an mRNA cancer vaccine.The trial is ongoing, but interim results found the treatment, known as Intismeran, met both ​its primary target of reducing cancer recurrence and ⁠its secondary goal ⁠of keeping cancers from ‌spreading to other parts of the body.In comments published on the U.K.-based Science Media Centre, Dr. Lennard Lee, a consultant medical oncologist and associate professor at Oxford, called the findings "significant" — noting they mark the first positive Phase 3 trial of a treatment combining immunotherapy and mRNA technology."That makes this an important moment for a field that scientists have been working towards for many years," Lee, who is not connected with the research, said. "Within 6 years of the pandemic, we have mRNA vaccines to treat cancer. "Still, Lee said that a significant amount of information has not yet been released."We do not yet have the magnitude of the Phase III benefit, the detailed subgroup analyses, quality-of-life data or mature overall-survival results," Lee wrote. "Those details will allow the scientific and clinical community to understand precisely how large the benefit is, which patients benefit most, and ultimately where this treatment might sit within routine melanoma care."The ​companies said they will present their results at an upcoming medical ​meeting and share ⁠them with regulators.U.S. FDA approves first mRNA flu shot from ModernaHealth Canada authorizes mRNA vaccine trial for Ebola virus causing huge outbreak in CongoIn a statement emailed to CBC News, Melanoma Canada CEO Falyn Katz also welcomed the results. "This personalized mRNA therapy could offer patients at high risk of recurrence or metastasis a powerful new way to prevent melanoma from returning or spreading," Katz wrote. "We look forward to seeing the full data and what this innovative treatment could mean for patients in Canada." 'Recognize and attack'The treatment combines Merck's Keytruda with a made-to-order mRNA vaccine from Moderna that is based on an analysis of mutations ⁠found in the patients' own tumours.Messenger-based RNA vaccines, which rose to prominence during the COVID-19 pandemic, give our cells instructions to help the immune system counter a pathogen. In this treatment, Lee said, tumour samples are used to single out abnormal proteins in cancer cells, called neoantigens. An mRNA vaccine can then train the immune system "to recognize and attack cancer cells" carrying those antigens."In simple terms, one treatment helps show the immune system what to look for, while the other helps release the brakes on the immune response," Lee said. WATCH | Health Canada approves mRNA Ebola vaccine trial:Canada approves trial for mRNA Ebola vaccineAugust 4|Duration 2:04Health Canada has approved a Phase 1 clinical trial for Moderna's potential mRNA vaccine for the Bundibugyo strain of Ebola. If found safe and effective, the vaccine would be used in future outbreaks of the virus.The trial enrolled 1,137 high-risk patients with Stage 2B-4 melanoma that had been surgically ‌removed.Volunteers were randomized to receive up to nine doses of Keytruda plus the personalized vaccine or Keytruda alone for about one year. The companies said no ​new safety signals have emerged in the trial.In January, the companies announced ⁠results of a mid-stage trial of the treatment showing that ⁠it reduced the risk of recurrence or death by ⁠49 per cent ⁠after five years.Shares of Moderna were up over 150 per cent in mid-morning trading, while Merck had risen over 10 per cent.According to the Canadian Cancer Society, around 11,300 people in Canada are likely to be diagnosed with melanoma this year, and an estimated 1,250 people will die from it. Melanoma Canada says melanoma is one of the most common types of cancer found among Canadians aged 15 to 29 and 30 to 49.In 2023, there were more than 1.5 million people in the U.S. living with melanoma, according to the U.S. National Cancer ⁠Institute. With files from CBC News