Figure 1. Schematic representation of the decision model. In panel A, the square node at the left represents the vaccination decision. The woman’s health thereafter is simulated by a Markov model. Each month, women are at risk of developing Human papillomavirus (HPV) infection, SIL (squamous intraepithelial lesions), or cervical cancer. Women who contract HPV may be infected by a low- or high-risk type. Panel B demonstrates cervical-cancer diagnosis, treatment, and natural history. Throughout a woman’s lifetime, her HPV, SIL, or cervical cancer status can be discovered either through development of symptoms or through routine Pap tests. Panel C shows that women who undergo a Pap test may test negative or positive for SIL.