Breast Cancer Vaccines
You’re probably familiar with traditional vaccines for polio, rubella, tuberculosis, and measles — diseases that have been nearly eliminated in the United States because so many people have been vaccinated.
The idea of a vaccine for breast cancer has been discussed by scientists for a number of years. Still, developing such a vaccine has been difficult because researchers need to find something in breast cancer cells the vaccine can target — like a protein or genetic mutation — that isn’t in healthy cells.
Thanks to innovative research and advances in genetic sequencing, scientists at several institutions think they have found breast cancer vaccine targets and are now conducting clinical trials.
How are breast cancer vaccines different from other vaccines?
Polio is caused by a virus. Tuberculosis is caused by a bacterium. Your immune system easily recognizes viruses and bacteria as foreign invaders. The vaccines for these diseases introduce your immune system to a weakened or killed version of the invader that doesn’t make you sick. When a vaccine enters your body, your immune system mounts a response and remembers the invader so it can fight it off again if it ever reappears.
Since breast cancer develops from your own cells (and isn’t caused by an organism), the immune system doesn’t recognize it as an invader. A breast cancer vaccine needs to target something in cancer cells that isn’t in healthy cells and then teach the immune system to recognize that target as an invader.
Current research focuses on two types of breast cancer vaccines: prevention vaccines and treatment vaccines.
Breast cancer prevention vaccines
Prevention vaccines have a goal of teaching your immune system to attack the earliest signs of cells that might turn into breast cancer.
Researchers at the Cleveland Clinic have started clinical trials on a breast cancer vaccine to prevent triple-negative breast cancer. The vaccine targets alpha-lactalbumin, a milk protein that’s only made in the mammary gland when a person who can get pregnant produces breast milk. Alpha-lactalbumin isn’t normally made without lactation and isn’t made by any other normal healthy tissues. And once a person is no longer of child-bearing age, the body stops making this protein. But research has shown that many triple-negative breast cancers make this protein. Since alpha-lactalbumin isn’t supposed to be made anymore, the theory is the immune system can be trained to see the protein as something harmful and attack it.
The researchers have started three, small phase I studies on a vaccine that targets alpha-lactalbumin to assess how well it’s tolerated. Phase I trials are the first clinical trials to test a new treatment in people.
The first study includes women who have completed treatment for early-stage, triple-negative breast cancer within the past three years. These women have no evidence of disease, but have a high risk of the cancer coming back, called recurrence by doctors.
The second study includes women who haven’t been diagnosed but have a high risk of developing breast cancer because of genetics and have decided to have a prophylactic mastectomy to lower their risk. These women have BRCA1, BRCA2, or PALB2 mutations.
The third study includes women diagnosed with early-stage, triple-negative breast cancer who received chemotherapy or radiation therapy before surgery and Keytruda (chemical name: pembrolizumab) after surgery. During surgery, doctors found that the treatments before surgery didn’t lead to a pathologic complete response (pCR), meaning the pre-surgery treatments didn’t destroy all the cancer cells. This means these women have a higher risk of recurrence.
In November 2024, the researchers announced that the vaccine was generally well tolerated and produced an immune response in most of the women who received it.
A phase II study to see how effective the vaccine is is expected to begin in late 2025 or early 2026.
Listen to an episode of The Breastcancer.org Podcast on breast cancer vaccine research with Dr. Justin Johnson, of the Cleveland Clinic.
Researchers at the University of Pennsylvania are studying a vaccine to prevent cancer in people with a BRCA1 or BRCA2 mutation, genetic mutations linked to a high risk of developing breast cancer. The researchers aim to vaccinate BRCA carriers who have not been diagnosed with cancer to see if the vaccine causes an immune response.
Breast cancer treatment vaccines
Much of the research on breast cancer vaccines is focused on cancer treatment vaccines. Treatment vaccines try to get the immune system to attack cancer cells.
Cancer treatment vaccines are made up of cancer cells, parts of cells, or antigens — the proteins on a foreign cell that allow the immune system to recognize it as “other.” In some cases, a person’s immune cells are taken from the body and exposed to these substances in the lab to create the vaccine. Once the vaccine is ready, it’s put back into the body to boost the immune system’s response to cancer cells.
Cancer treatment vaccines may take months to produce a noticeable immune system response, so they may be most useful to reduce the risk of the cancer coming back after surgery and other treatments.
Researchers at the University of Washington’s Cancer Vaccine Institute have started a phase I study to test a vaccine to control metastatic, HER2-positive breast cancer. Initial results show that the vaccine caused an immune response in the people who received it.
Researchers at the University of Pittsburgh are testing a vaccine to treat DCIS in a phase I study, with the goal of training the immune system to eliminate DCIS cells before they become invasive breast cancer. The vaccine relies on the MUC1 protein, which can activate the immune system. People participating in the study will receive three doses of the vaccine. The researchers will then assess the immune response.
When will a breast cancer vaccine be available?
At this time, no breast cancer vaccines have been approved by the U.S. Food and Drug Administration to prevent or treat breast cancer. All the current clinical trials of cancer vaccines are in the earliest stage (phase I) and include a small number of participants (fewer than 50 people). Many of these trials are still asking participants to join and haven’t reported any result yet. So it’s difficult to say when a vaccine might be available.
The results of some of these small trials suggest that the vaccines are causing an immune response, but it’s too early to tell if that immune response is big enough to make the vaccines effective.
If you’re interested in being part of a study on a breast cancer vaccine, there’s information online about how to find a clinical trial. You can also ask your doctor or search for “breast cancer vaccine” at clinicaltrials.gov.
— Last updated on June 30, 2025 at 3:51 PM