Cervical
infections by approximately 15
cancer-associated (carcinogenic) human papillomavirus (HPV) genotypes cause virtually all
cervical cancer and its immediate precursor lesions worldwide. Prophylactic
vaccines against human papillomavirus (HPV) types HPV16 and HP18, which cause 70% of
cervical cancer worldwide, hold great promise for reducing the burden of
cervical cancer worldwide. However, current
HPV vaccines prevent future
infections and related cervical abnormalities and do not treat pre-existing
HPV infections. In the U.S.,
HPV vaccine introduction should be considered in the context of a very successful
cervical cancer screening program that has reduced the rates of
cervical cancer by 75% or more. Thus,
HPV vaccines will only prevent an incremental number of additional
cervical cancers in the U.S. The introduction of
HPV vaccines can also prevent other HPV-related sequelae, most importantly
cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3), which precede the development of
cervical cancer and require clinical follow-up and treatment. Examining data from 7 clinical centers in the U.S., the median age of CIN2/3 is typically between 25 and 30 years of age in 2007; if screen-detected CIN2/3 develops on average 5-10 years after the causal
infection is acquired, HPV vaccination will only prevent a significant proportion of CIN2/3 if it is given to women before the age of 26 and more so if given to women 18 and younger. It is increasingly evident that prophylactic
HPV vaccines will provide the greatest public health or population benefit only when delivered to adolescent, mostly HPV-naive women.