Immunizing against Anogenital Cancer: HPV Vaccines

Most of us are familiar with foot and hand warts caused by the skin tropic human papillomaviruses (HPV). However, it is less well recognized that infection with HPV types that replicate in the anogenital mucosa is the most prevalent sexually transmitted disease in the world. Indeed, a recent estimate suggests that 80%–90% of the sexually active population is exposed during their lifetime to mucosal HPV [1]. Of the more than 40 genotypes of mucosal HPV, most result in benign and transient disease, such as genital warts caused by HPV types 6 and 11. However, 15 HPV genotypes (e.g., HPV types 16 and 18) are classified as high-risk because they are causal agents of human cancers [2]. Almost all of the half million cervical cancer cases that occur worldwide each year are related to infection with high-risk HPV (hrHPV) [4]. High-risk HPVs, most especially HPV16, are also implicated in the development of some anal, oropharyngeal, vaginal, vulval, and penile cancers. Within a given population, the most prevalent hrHPV genotype varies with geographical location [1–3]. Combined, all of the hrHPVs are responsible for approximately 5% of all cancers worldwide (10% in women) [1–3]. HPV infection is a significant health burden on the United States economy, costing approximately US $7.6 billion per year for screening (Pap smear) and cervical cancer treatment [4]. Recommendations for the current vaccines are for routine inoculation of females 13–26 years of age as well as males 13–21 years of age. The vaccines are most effective when administered prior to potential virus exposure (i.e., before commencement of sexual activity) [5]. Vaccination is the most effective strategy to prevent these cancers and associated morbidities [3–5].