For decades, researchers have sought to develop vaccines to treat cancer, but progress has been limited by the complexity of the disease, the diversity of cancer types and biological differences among individual patients.
Now, a personalized cancer vaccine has succeeded in a phase 3 trial for the first time.
Merck and Moderna’s intismeran autogene vaccine, given with the immunotherapy drug Keytruda, kept advanced melanoma from returning or spreading longer than Keytruda alone in a 1,137-patient trial.
The milestone comes as the National Institutes of Health plans to launch a national public-private initiative in December to accelerate cancer vaccine research.
Merck and Moderna’s latest findings offer new evidence for personalized cancer vaccines, but questions remain about their overall survival benefits and the path toward broader clinical use.
What are cancer vaccines?
Cancer vaccines fall into two broad groups: preventive vaccines, which protect against infections that can cause cancer, and therapeutic vaccines, which stimulate the immune system to attack existing cancers.
Vaccines that prevent cancers caused by viruses have been in use for decades, with hepatitis B vaccines first approved by the FDA in 1981 and HPV vaccines first approved in 2006.
HPV vaccines are the most established preventive cancer vaccines, with vaccination capable of preventing more than 90% of HPV-related cancers, according to the CDC. The World Health Organization’s Strategic Advisory Group of Experts on Immunization now considers a single dose the most efficient way to prevent cervical cancer in girls ages 9 to 14.
However, only an estimated 33% of girls targeted by HPV vaccination programs worldwide received a first dose in 2025, according to WHO data. Globally, an estimated 24% of girls had completed the recommended vaccination schedule by age 15, well below the WHO’s 90% target.
Researchers are now testing preventive vaccines for cancers not tied to infection.
In a phase 1 trial led by researchers at Baltimore-based Johns Hopkins University, a vaccine targeting six common KRAS mutations produced immune responses in 18 of 20 people who were at high risk of developing pancreatic cancer, with vaccine-induced immune cells detectable for up to two years.
FDA-approved immunotherapies used to treat cancer include Provenge, a therapeutic vaccine for advanced prostate cancer; Imlygic, an oncolytic virus therapy for certain melanoma tumors; and BCG, a tuberculosis vaccine used to treat early-stage bladder cancer.
More recent research has focused on personalized cancer vaccines, which are developed using an individual patient’s own tumor and often administered after surgery to reduce the risk of recurrence.
How do personalized cancer vaccines work?
Personalized vaccines are designed around specific mutations found in one patient’s tumor. Some of those mutations produce abnormal proteins, called neoantigens, that the immune system can learn to recognize.
Intismeran, Merck and Moderna’s mRNA vaccine, can be customized to target up to 34 neoantigens, according to the Cancer Research Institute, and is paired with Merck’s immunotherapy drug Keytruda.
Because each patient’s intismeran vaccine is custom-made, the process takes about six weeks from tumor sequencing to hospital delivery, though Merck CEO Rob Davis expects that window to shrink.
Are cancer vaccines effective?
Merck and Moderna’s phase 3 trial of intismeran and Keytruda — known as INTerpath-001 — enrolled patients with stage 2B to 4 cutaneous melanoma that had been fully removed by surgery. The companies are scheduled to present detailed efficacy results Oct. 24 at the European Society for Medical Oncology Congress 2026 in Madrid.
The most detailed efficacy data available for the intismeran and Keytruda combination comes from an earlier phase 2b trial known as KEYNOTE-942. Among 157 patients with high-risk melanoma, adding intismeran to Keytruda cut the risk of recurrence or death by 49% and the risk of distant spread or death by 59% after five years.
Smaller studies at academic cancer centers have also shown promising results in pancreatic, kidney and brain cancers.
In a 16-patient study at New York City-based Memorial Sloan Kettering Cancer Center, half the patients mounted an immune response to BioNTech’s personalized vaccine, autogene cevumeran. Seven of those eight were alive up to six years after treatment, compared with two of the eight patients who did not respond.
In a phase 1 trial at Boston-based Dana-Farber Cancer Institute, all nine kidney cancer patients who received a personalized vaccine were cancer-free after 40 months.
Two-thirds of nine glioblastoma patients who received a personalized DNA vaccine as part of a phase 1 trial at St. Louis-based Siteman Cancer Center had no cancer progression six months after surgery. One patient remains cancer-free about five years after her diagnosis.
Not all cancer vaccine trials have produced promising results.
BioNTech ended a phase 2 colorectal cancer trial of autogene cevumeran Aug. 28 after a recommendation from an independent data safety monitoring board. The vaccine’s pancreatic cancer trial continues.
On Oct. 13, BioNTech said a separate mRNA cancer immunotherapy, BNT113, did not significantly improve progression-free survival in a phase 2/3 head and neck cancer trial.
Is the government funding cancer vaccine research?
The NIH is organizing a national partnership modeled on the federal effort to develop COVID-19 vaccines, with the goal of expanding personalized cancer vaccine research. The initiative would bring together the NIH, the Foundation for the NIH, drugmakers, researchers and advocacy groups.
Initial research will focus on pancreatic, liver and colorectal cancers, along with certain pediatric tumors. Small, early-stage studies are expected to take about three years, followed by larger trials lasting at least four years across a national network of sites.
The initiative follows HHS’ August 2025 decision to cancel nearly $500 million in federal contracts associated with mRNA vaccine development through the Biomedical Advanced Research and Development Authority, affecting 22 projects focused largely on respiratory infections.
What’s next for cancer vaccines?
Merck and Moderna will present detailed results from the phase 3 INTerpath-001 trial Oct. 24 at ESMO. Moderna will also present early results from a pancreatic cancer study of intismeran Oct. 25 and the design of a phase 3 trial in early-stage lung cancer Oct. 26.
Beyond the upcoming presentations, questions remain about whether cancer vaccines improve overall survival, how well they work across different cancer types and when they could become widely available. Cost and manufacturing timelines will also be important factors in their broader adoption.
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