Cancer vaccines are medicines that spur the immune system’s natural defenses against cancer. They belong to a class of substances known as biological response modifiers, which strengthen or stimulate a basic bodily process – in this case, the immune system’s ability to detect and attack cancer cells.
There are two broad types of cancer vaccines: Preventive vaccines, which are intended to prevent cancer from developing, and therapeutic vaccines, which treat an existing cancer.
The U.S. Food and Drug Administration has approved two preventive vaccines, Gardasil and Cervarix, for the prevention of cervical cancer. These work by the same general principle as preventive vaccines for measles and chicken pox. By rousing the immune system’s response to a harmful virus, they guard against infection from the virus and from development of the disease it triggers. Such vaccines do not work once a cancer has become established.
Gardasil and Cervarix prevent infection by two strains of the human papillomavirus (HPV) that cause about 70 percent of cervical cancer cases worldwide. The same two strains also cause some vaginal, vulvar, anal, penile and oropharyngeal cancers (which arise in the middle of the throat). Gardasil also protects against infection by two additional types of HPV, which give rise to about 90 percent of cases of genital warts in males and females but don’t cause cervical cancer.
The FDA has also approved a vaccine that protects against infection by the hepatitis B virus (HBV), chronic instances of which can lead to liver cancer. Most children in the United States are vaccinated against HBV shortly after birth.
In 2010, Provenge became the first therapeutic cancer vaccine to receive FDA approval. The vaccine, which is used for treating some men with metastatic prostate cancer, is made by collecting immune system cells called antigen-presenting cells (APCs) from a patient’s blood and growing them in the presence of a protein that helps the immune system identify and hunt down prostate cancer cells. The enhanced APCs are then injected in the patient.
Research and development of new therapeutic and preventive cancer vaccines are underway at research centers around the world, focusing on a wide range of cancers. Many of the trials of therapeutic vaccines combine the vaccines with other treatment methods to improve their effectiveness.
Research into the immune system has revealed some of the ways that cancer cells can fend off an attack from the immune system. Agents that interfere with that process are showing great promise in a variety of cancers, but they work only if a patient’s immune system has already mobilized against the cancer. Using a vaccine to spark the immune system’s response to cancer may increase the number of patients who benefit from these agents.