Cancer vaccines fall into two broad categories: preventive vaccines that stop cancer from developing, and therapeutic vaccines that treat existing cancer. Within the therapeutic category, there are four main platform types: peptide vaccines, dendritic cell vaccines, mRNA vaccines, and viral vector vaccines. Each uses a different strategy to teach your immune system to recognize and attack cancer cells.
Preventive vs. Therapeutic Cancer Vaccines
Preventive cancer vaccines work like traditional vaccines. They protect you from viruses that can cause cancer down the line. The two FDA-approved examples are the hepatitis B vaccine and the HPV vaccine. By blocking viral infections before they take hold, these vaccines interrupt the chain of events that could eventually lead to uncontrolled cell growth. They don’t treat cancer directly; they eliminate the conditions that give rise to it.
Therapeutic cancer vaccines take the opposite approach. They’re designed for people who already have cancer. These vaccines train your immune system to find cells carrying specific markers, called antigens, that are linked to a particular cancer type. The goal is to stop a tumor from growing or spreading, destroy cancer cells that remain after surgery or radiation, or prevent a cancer from coming back after treatment. Only two therapeutic vaccines have been approved across all cancer types so far: one for bladder cancer (BCG) and one for prostate cancer (sipuleucel-T). But dozens more are in clinical trials using the four platform technologies below.
1. Peptide Vaccines
Peptide vaccines use small protein fragments from cancer cells to trigger an immune response. These fragments are synthetic copies of the markers found on the surface of tumor cells. Once injected, immune cells called dendritic cells pick up these protein fragments, process them, and display them to your T cells. This activates two types of T cells: helper T cells that coordinate the broader immune response, and killer T cells that hunt down and destroy any cell displaying that same marker.
The appeal of peptide vaccines is their simplicity and precision. Researchers can select specific protein targets that appear on cancer cells but not on healthy tissue, reducing the risk of collateral damage. One example in development uses fragments of a protein called survivin, which is found in a large proportion of cancer cells but is normally invisible to the immune system. The vaccine was shown to activate both helper and killer T cell responses regardless of a patient’s genetic background, which is important because many cancer treatments only work in people with certain immune system genes.
The limitation is that protein fragments alone aren’t always enough to provoke a strong immune reaction. Peptide vaccines typically need to be combined with an adjuvant, a substance that amplifies the immune system’s response, to be effective.
2. Dendritic Cell Vaccines
Dendritic cells are your immune system’s scouts. They detect threats, collect information about them, and relay that information to T cells so they can mount an attack. Dendritic cell vaccines take advantage of this natural role by loading these scout cells with cancer-specific markers outside the body, then reinjecting them to kick-start a targeted immune response.
Sipuleucel-T, approved in 2010 for advanced prostate cancer, was the first dendritic cell cancer vaccine to receive FDA approval. The process is personalized: a patient’s own immune cells are collected, exposed to a protein found on prostate cancer cells, and then returned to the body. This primes the immune system to recognize and attack prostate tumors.
The manufacturing process is complex and time-consuming because it requires collecting and culturing each patient’s cells individually. Researchers are working on improved methods to grow the three major subtypes of dendritic cells more efficiently, but for now, the labor-intensive production remains a bottleneck.
3. mRNA Vaccines
mRNA cancer vaccines use the same core technology that powered the COVID-19 vaccines from Pfizer and Moderna, but with a twist: instead of encoding a viral protein, the mRNA carries instructions for proteins unique to an individual patient’s tumor. These mutated proteins, called neoantigens, act like an activated security alarm, alerting the immune system that cells displaying them are threats that need to be destroyed.
The process starts with intensive genetic analysis of a patient’s tumor sample, typically collected during surgery. Researchers identify the specific mutations on that patient’s cancer cells, then construct custom mRNA sequences for up to 20 target neoantigens per vaccine. BioNTech, the German company behind one of the COVID vaccines, has partnered with Memorial Sloan Kettering on a personalized mRNA vaccine for pancreatic cancer called autogene cevumeran. Early trial results showed that patients who developed a strong immune response to their vaccine had significantly delayed cancer recurrence.
The strength of mRNA vaccines is speed and flexibility. Once a tumor’s genetic profile is mapped, manufacturing a custom vaccine takes weeks rather than months. The mRNA also naturally triggers some immune activation on its own, which helps amplify the response.
4. Viral Vector Vaccines
Viral vector vaccines use genetically modified viruses to deliver cancer-specific markers directly into your cells. The viruses are engineered so they can’t cause disease, but they retain their natural ability to enter cells and trigger a strong immune reaction. Common viral vectors include adenoviruses (modified cold viruses), poxviruses, and others derived from chimpanzee or gorilla adenoviruses.
The key advantage of viral vectors is potency. Viruses naturally activate your innate immune system through patterns your body has evolved to recognize as foreign, which means these vaccines can provoke powerful immune responses without needing additional adjuvants. They can also encode multiple neoantigens at once, which helps address one of cancer’s trickiest defenses: tumor cells within the same patient can carry different mutations, so targeting several markers simultaneously reduces the chance that some cancer cells escape detection.
One particularly effective strategy is the “prime-boost” approach, where two different viral vectors are used in sequence. Clinical studies have consistently shown that priming the immune system with one type of virus, then boosting it with a different one, produces stronger T cell responses than repeating the same vaccine. A common combination pairs a great ape-derived adenovirus for the first dose with a modified vaccinia virus for the boost.
How Effective Are Cancer Vaccines So Far?
The honest picture is mixed. A large review of 187 clinical trials of therapeutic cancer vaccines found that only 19% used a clinical outcome like survival or remission as their primary measure of success. Of those, roughly a third met their goal. Among the 33 randomized trials reviewed, not a single vaccine demonstrated an improvement in overall survival.
That sounds discouraging, but context matters. Many of these trials tested earlier-generation vaccines in patients with very advanced disease. The newer personalized approaches, particularly mRNA and viral vector vaccines targeting patient-specific neoantigens, represent a fundamentally different strategy. These are now being tested earlier in the course of disease, often right after surgery, when the immune system has a better chance of eliminating remaining cancer cells before they establish new tumors. Results from those trials are still maturing, but the early signals from pancreatic and kidney cancer studies have been strong enough to push several vaccines into larger-scale testing.