Human Papillomavirus (HPV) Infection
More than 100 types of HPV exist, more than 40 of which can infect the genital area. Most HPV infections are asymptomatic, unrecognized, or subclinical. Oncogenic, or high-risk HPV types (e.g., HPV types 16 and 18), are the cause of cervical cancers. These HPV types are also associated with other anogenital cancers in men and women, including penile, vulvar, vaginal, and anal cancer, as well a subset of oropharyngeal cancers (404). Nononcogenic, or low-risk HPV types (e.g., HPV types 6 and 11), are the cause of genital warts and recurrent respiratory papillomatosis. Asymptomatic genital HPV infection is common and usually self-limited; it is estimated that more than 50% of sexually active persons become infected at least once in their lifetime (405). Persistent oncogenic HPV infection is the strongest risk factor for development of precancers and cancers.
HPV tests are available for women aged >30 years undergoing cervical cancer screening. These tests should not be used for men, for women <20 years of age, or as a general test for STDs. These HPV tests detect viral nucleic acid (i.e., DNA or RNA) or capsid protein. Four tests have been approved by the FDA for use in the United States: the HC II High-Risk HPV test (Qiagen), HC II Low-Risk HPV test (Qiagen), Cervista HPV 16/18 test, and Cervista HPV High-Risk test (Hologics).
Treatment is directed to the macroscopic (i.e., genital warts) or pathologic (i.e, precancerous) lesions caused by infection. Subclinical genital HPV infection typically clears spontaneously, and therefore specific antiviral therapy is not recommended to eradicate HPV infection. In the absence of lesions, treatment is not recommended for subclinical genital HPV infection whether it is diagnosed by colposcopy, acetic acid application, or by laboratory tests for HPV DNA. Treatment also is not recommended for cervical intraepithelial neoplasia 1 (CIN1).
Two HPV vaccines are licensed in the United States: a bivalent vaccine (Cervarix) containing HPV types 16 and 18 and a quadrivalent vaccine (Gardasil) vaccine containing HPV types 6, 11, 16, and 18. Both vaccines offer protection against the HPV types that cause 70% of cervical cancers (i.e., types 16 and 18), and the quadrivalent HPV vaccine also protects against the types that cause 90% of genital warts (i.e., types 6 and 11). Either vaccine can be administered to girls aged 11–12 years and can be administered to those as young as 9 years of age (15,16); girls and women ages 13–26 years who have not started or completed the vaccine series also should receive the vaccine. HPV vaccine is indicated for girls in this the onset of sexual activity. The quadrivalent (Gardasil) HPV vaccine can also be used in males aged 9–26 years to prevent genital warts (17). Administering the vaccine to boys before the onset of sexual activity is optimal. Both HPV vaccines are administered as a 3-dose series of IM injections over a 6-month period, with the second and third doses given 1–2 and then 6 months after the first dose. Ideally, the same vaccine product should be used for the entire 3-dose series. HPV vaccine is available for eligible children and adolescents aged <19 years through the Vaccines for Children (VFC) program (available by calling CDC INFO [800-232-4636]).
Women who have received HPV vaccine should continue routine cervical cancer screening because 30% of cervical cancers are caused by HPV types other than 16 or 18. In the United States, the vaccines are not licensed or recommended for use in women >26 years of age. No published data are available on the effectiveness, programmatic requirements, or cost-effectiveness of administering the HPV vaccine in STD clinic settings.