Human papilloma virus (HPV) vaccines are vaccines that prevent infection by certain types of human papillomavirus. Available vaccines protect against either two, four, or nine types of HPV. All vaccines protect against at least HPV 16 and 18 that cause the greatest risk of cervical cancer. It is estimated that they may prevent 70% of cervical cancer, 80% of anal cancer, 60% of vaginal cancer, 40% of vulvar cancer, and possibly some mouth cancer. They additionally prevent some genital warts with the vaccines against 4 and 9 HPV types providing greater protection.