While some viruses have been identified as the cause of cancer in humans, viruses can also be used to control and even prevent cancer. This is due to the fact that some viruses are naturally able to target and destroy cancer cells. 3.1 Cancer vaccines Vaccines can be used as a preventative measure against cancer. The most common way to use viruses to prevent cancer in the first place is by vaccination against viruses associated with cancer. Vaccines against hepatitis B virus, associated with liver cancer, and human papilloma virus, associated with cervical cancer, are already widely used (beneficial use of the virus). Approximately 12,000 women are diagnosed with cervical cancer and 4,000 women die from the disease worldwide. United States annually (2012 HPV vaccine). There are currently two vaccines available to prevent the human papillomavirus (HPV) that causes most cervical cancers: the bivalent vaccine (Cervarix) and the quadrivalent vaccine (Gardasil). Vaccines target and kill the cells that most commonly cause cervical cancer. Both bivalent and quadrivalent vaccines are highly effective at preventing target HPV types, as well as HPV-associated symptoms (HPV 2012). According to the researchers, the vaccine is long-lasting. It has been shown to last up to six years without any weakening of its protection over time (HPV 2012). It is 100% effective where the person taking the vaccine has not been sexually active in their life and is therefore offered in many countries as part of school vaccination programs (Gostout)3.2 VirotherapyIt is possible to directly use the cell-destroying effects of virus instead of relying on the immune system... in the center of the card... red in a systematic way (Beneficial use of the virus). This means that the active, cytotoxic form of the drug is produced only where the corresponding enzyme is present and active. The example often given to explain this process is the herpes simplex virus adenovirus-expressing thymidine kinase (TK) enzyme. This can be used together with the systemic administration of a drug called ganiclovir, which in the cell's enzymes is converted by TK into its active form. This process is used in the treatment of HIV (beneficial use of the virus).3.4 Future for cancer therapyThe future of cancer therapy certainly looks more promising since viruses have already been used to prevent cancer through vaccinations but also through techniques such as virotherapy and prodrug therapy, which are safer and have fewer side effects than current cancer treatments such as chemotherapy.