Most of us know about vaccines given to healthy people to help prevent infections, such as measles and chicken pox. These vaccines use weakened or killed germs like viruses or bacteria to start an immune response in the body. Getting the immune system ready to defend against these germs helps keep people from getting infections.
Most cancer vaccines work the same way, but they make the person’s immune system attack cancer cells. The goal is to help treat cancer or to help keep it from coming back after other treatments. But there are also some vaccines that may actually help prevent certain cancers.
Vaccines to help prevent cancer
Many people might not realize it, but some cancers are caused by viruses. Vaccines that help protect against infections with these viruses might also help prevent some of these cancers.
- Some strains of the human papilloma virus (HPV) have been linked to cervical, anal, throat, and some other cancers. Vaccines against HPV may help protect against some of these cancers.
- People who have chronic (long-term) infections with the hepatitis B virus (HBV) are at higher risk for liver cancer. Getting the vaccine to help prevent HBV infection may therefore lower some people’s risk of getting liver cancer.
These are traditional vaccines that target the viruses that can cause certain cancers. They may help protect against some cancers, but they don’t target cancer cells directly.
These types of vaccines are only useful for cancers known to be caused by infections. But most cancers, such as colorectal, lung, prostate, and breast cancers, are not thought to be caused by infections. Doctors are not yet sure if it’s possible to make vaccines to prevent these other cancers. Some researchers are now trying, but this research is still in very early stages. Even if such vaccines prove to be possible, it will be many years before they become available.
Vaccines to help treat cancer
Cancer treatment vaccines are different from the vaccines that work against viruses. These vaccines try to get the immune system to mount an attack against cancer cells in the body. Instead of preventing disease, they are meant to get the immune system to attack a disease that already exists.
Some cancer treatment vaccines are made up of cancer cells, parts of cells, or pure antigens. Sometimes a patient’s own immune cells are removed and exposed to these substances in the lab to create the vaccine. Once the vaccine is ready, it’s injected into the body to increase the immune response against cancer cells.
Vaccines are often combined with other substances or cells called adjuvants that help boost the immune response even further.
Cancer vaccines cause the immune system to attack cells with one or more specific antigens. Because the immune system has special cells for memory, it’s hoped that the vaccine might continue to work long after it’s given.
This is the only vaccine approved in the US to treat cancer so far. It’s used to treat advanced prostate cancer that is no longer being helped by hormone therapy.
For this vaccine, immune system cells are removed from the patient’s blood and sent to a lab. There they are exposed to chemicals that turn them into special immune cells called dendritic cells. They are also exposed to a protein called prostatic acid phosphatase (PAP), which should produce an immune response against prostate cancer cells.
The dendritic cells are then given back to the patient by infusion into a vein (IV). This process is repeated twice more, 2 weeks apart, so that the patient gets 3 doses of cells. Back in the body, the dendritic cells help other immune system cells attack the prostate cancer.
Although the vaccine doesn’t cure prostate cancer, it has been shown to help extend patients’ lives by several months on average. Studies to see if this vaccine can help men with less advanced prostate cancer are now being done.
Side effects are usually mild and can include fever, chills, fatigue, back and joint pain, nausea, and headache. A few men may have more severe symptoms, including problems breathing and high blood pressure.
Many different types of cancer vaccines have shown some promise in clinical trials, but they are not yet approved in the United States to treat cancer.