Cancer Vaccines and Their Side Effects
Most people are familiar with vaccines used to prevent infections like measles and chickenpox. They work by training the immune system to recognize and respond to harmful germs. But there are also some vaccines that can also be designed to help the immune system find and attack cancer cells. Cancer vaccines are currently available for some prostate and bladder cancers, and more are being researched.
What are cancer vaccines?
Cancer vaccines are substances made in the lab that are used to make the body’s natural defense mechanisms stronger to protect itself. Depending on the type of vaccine, some can be used as cancer treatment and other times, as cancer prevention (such as the human papilloma virus, or HPV, vaccine).
How are vaccines used to treat cancer?
Vaccines used to treat cancer are called therapeutic cancer vaccines. Instead of preventing disease, they are meant to get the immune system to attack a disease a person already has.
Therapeutic cancer vaccines can work by:
- Keeping cancer from coming back
- Destroying any cancer cells still in the body after treatments end
- Stopping a tumor from growing or spreading
Therapeutic cancer vaccines teach the immune system to find and attack cancer cells that have certain markers, called antigens. The immune system can remember these markers, so the vaccine might keep working long after it’s given.
What are cancer vaccines made of?
Some cancer vaccines are made from cancer cells, parts of cells, or pure antigens (certain proteins on the cancer cells). Sometimes a person’s own immune cells are removed and exposed to these substances in the lab to create the vaccine.
Vaccines are often combined with other substances or cells called adjuvants that help boost the immune response even further.
Other vaccines are made from bacteria or viruses that can trigger a specific immune response.
Types of therapeutic cancer vaccines
Several therapeutic cancer vaccines have been approved by the US Food and Drug Administration (FDA). They include:
Sipuleucel-T (Provenge) is used to treat advanced prostate cancer that is no longer being helped by hormone therapy. This vaccine is made by:
- Removing immune cells (white blood cells) from your blood
- Combining them with a protein from prostate cancer cells
- Giving them back to you by infusing them into a vein (IV)
The process is repeated a total of 3 times. The cells then work to help your immune system attack the prostate cancer cells. While it hasn’t been shown to cure cancer, it can help some people live longer.
Bacillus Calmette-Guerin (BCG) is used to treat early-stage bladder cancer. It’s made from a type of bacteria related to the one that causes tuberculosis, but it doesn’t cause someone to get sick. It is given through an intravesical infusion directly into the bladder, where it stimulates the immune system to attack the bladder cancer cells.
Nadofaragene firadenovec (Adstiladrin) is a gene therapy that works much like a cancer vaccine to treat early-stage bladder cancers that have progressed after BCG therapy. It uses a virus to deliver a gene that stimulates bladder cells to produce interferon alfa-2b, a protein that helps the immune system attack cancer cells. Like BCG, it’s given through an intravesical infusion directly into the bladder.
Side effects of cancer vaccines
Side effects of cancer vaccines differ from person to person and depend on the type of vaccine that is given. Some common side effects include:
Infusion reactions most often start suddenly, usually within minutes to hours after taking the immunotherapy. They may include hives (raised skin welts that often go away in a day or so) and intense itching. An allergic or infusion reaction often includes other serious symptoms such as trouble breathing, dizziness, tightness in the throat or chest, or swelling of the lips or tongue.
Other, more serious side effects occur less often and include:
- Difficulty breathing
- High blood pressure
- Stroke
Your cancer care team will watch you closely during treatment and will check you often. Side effects can and should be treated as early as possible. It’s important to tell your cancer care team about any changes in how you feel or anything you notice that’s new or unusual. Tell them right away so they can treat any problems and try to keep them from getting worse.
Why don’t cancer vaccines work for everyone?
Making therapeutic cancer vaccines that work is a challenge because:
Cancer cells suppress the immune system. This is how cancer begins and grows in the first place. Researchers are using adjuvants in vaccines to try to fix this problem.
Cancer cells start from a person's own healthy cells. As a result, cancer cells may not look harmful to the immune system. The immune system may ignore the cells instead of finding and attacking them.
Larger or more advanced tumors are hard to get rid of using only a vaccine. This is one reason doctors often give a cancer vaccine along with other treatment.
People who are sick or older can have weak immune systems. Their bodies may not be able to produce a strong immune response after they receive a vaccine. That limits how well a vaccine works. Also, some cancer treatments may weaken a person's immune system. This limits how well the body can respond to a vaccine.
For these reasons, some researchers think cancer treatment vaccines may work better for smaller tumors or cancer in its early stages.
Ongoing therapeutic cancer vaccine research
Cancer vaccine research is quickly changing. Researchers are finding improved ways to identify targets for new therapeutic cancer vaccines that can work better to destroy cancer cells. This includes work in mRNA technology. They also are looking for ways to combine therapeutic cancer vaccines with other forms of cancer treatments, including another type of immunotherapy called checkpoint inhibitor therapy, to help the immune system work even better.
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- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
American Society of Clinical Oncology (ASCO). What are cancer vaccines? Accessed at cancer.net. Content is no longer available.
American Society of Clinical Oncology (ASCO). What is immunotherapy? Accessed at cancer.net. Content is no longer available.
Makker S, Glley C, Bennett CL. Cancer vaccines: From an immunology perspective. Immunotherapy Advances. 2024; 4(1), ltad030, doi.org/10.1093/immadv/ltad030
National Cancer Institute (NCI). Cancer treatment vaccines. Updated September 24, 2019. Accessed from https://www.cancer.gov/about-cancer/treatment/types/immunotherapy/cancer-treatment-vaccines on August 7, 2025.
Shoushtari AN, Johnson DB. Principles of cancer immunotherapy. UpToDate. 2024. Accessed at https://www.uptodate.com/contents/principles-of-cancer-immunotherapy on August 7, 2025.
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Last Revised: July 7, 2025
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