Cervical cancer
Cervical cancer nearly always involves human papillomavirus (HPV) infection. HPV is a virus with numerous strains, several of which predispose to precancerous changes in the cervical epithelium, particularly in the transformation zone, which is the most common area for cervical cancer to start. HPV vaccines, such as Gardasil and Cervarix, reduce the incidence of cervical cancer, by inoculating against the viral strains involved in cancer development.