A cancer vaccine either treats existing cancer or prevents development of a cancer. Vaccines that treat existing cancer are known as therapeutic cancer vaccines. Many of the cancer vaccines are Autologous being prepared from samples taken from the patient and are specific to that patient. Some research indicates that tumors form when the immune system fails to destroy them. Some types of cancer such as cervical cancer and some liver cancers are caused by viruses. Traditional vaccines against those viruses, such as HPV vaccine and hepatitis B vaccine prevent those types of cancer. Other cancers are to some extent caused by bacterial infections for instance stomach cancer by helicobacter pylori. Traditional vaccines against cancer-causing bacteria or oncobacteria are discussed in this session along with other cancer vaccines.