Human papillomavirus (HPV) is a group of more than 100 viral DNA strains that infect epithelium and mucous membranes. More than 40 strains are known to cause infection in the male and female genital tracts, and at least 13 are identified as high-risk oncogenic strains.1 The best known strains are HPV types 6, 11, 16, and 18. HPV types 6 and 11 are associated with genital warts, or condyloma acuminata, in both sexes. HPV types 16 and 18 are most notorious for causing cervical, vulvar, and vaginal cancers in women.2
Presently affecting approximately 20 million people in the United States, human papillomavirus is the most common sexually transmitted infection. Of the 6 million newly diagnosed cases of HPV every year, about 74% are diagnosed in 15- to 24-year-olds.2 An estimated 50% to 80% of men and women who are sexually active will contract HPV at some time in their lives, often more than one strain.2,3
HPV TRANSMISSION AND RISK FACTORS
HPV infections are easily spread from one person to another through sexual activity, most often through vaginal, anal, or oral sex or through genital-to-genital contact. The disease can be transmitted between both heterosexual and homosexual partners. Among the general US population, the prevalence of HPV in anogenital sites and semen in males ages 18 to 40 years is 51%.4 HPV is quickly acquired after the first sexual encounter; up to 20% of females 18 years or younger will be infected by at least one of the oncogenic HPV strains, with comparable results in males of the same age range.4 Oral HPV infection is also associated with having an increased numbers of open-mouthed kissing partners.5 Risk factors include having multiple oral, anal, and/or vaginal sex partners; being a homosexual or bisexual man; having HIV infection or immunosuppression; increasing age; and marijuana use.1-6
OTHER CANCERS CAUSED
BY HPV
At least one of the oncogenic strains of HPV is present in the vast majority of cervical cancers. In recent years, however, high-risk types of HPV have been discovered to cause 30% to 40% of oropharyngeal cancers—more specifically, squamous cell carcinomas of the lingual and palatine tonsils, where HPV type 16 is most strongly associated with these cancers in up to 93% of cases.5,6 HPV also causes 40% of cancers of the external genitalia and up to 90% of cancers involving the anal canal.6
THE HPV VACCINE
Gardasil is a recombinant quadrivalent vaccine against HPV types 6, 11, 16, and 18, while Cervarix is a recombinant bivalent vaccine against HPV types 16 and 18. Only Gardasil is FDA-approved for both males and females aged 9 to 26 years.
Gardasil is currently specified for protection against cervical cancer and most genital warts. The vaccine should be administered intramuscularly as a 0.5-mL dose and then repeated at 2 and 6 months. The patient should be observed for 15 minutes after vaccine administration for postvaccination syncope.7 Other possible reactions include pain, swelling, redness at the site of injection, and rare instances of anaphylactic allergic reactions, especially in those allergic to yeast.7
THE BOTTOM LINE
The HPV vaccine is only indicated for the prevention of cervical cancer in females and genital warts in both males and females. However, the two high-risk, oncogenic HPV strains that the vaccine protects against may also cause male-specific penile cancers and other serious cancers of the anal canal and oropharynx. Vaccinated boys aged 10 to 14 years build a more robust immunity against HPV compared to girls of the same age and boys older than 15 years who have also received the vaccine.4 Therefore, immunizing males prior to sexual activity may optimally enhance the vaccine's protection against HPV and prevent these cancers. JAAPA
Jessica Stabb is a student in the Hahnemann PA program, College of Nursing and Health Professions, Drexel University, Philadelphia, Pennsylvania. Rebecca Buckley is a faculty member in the Hahnemann physician assistant program. The authors have indicated no relationships to disclose relating to the content of this article.
Mary L. Hewett, PA-C, MS, department editor
REFERENCES
1. Dunne EF, Nielson CM, Hagensee ME, et al. HPV 6/11, 16, 18 seroprevalence in men in two US cities. Sex Transm Dis. 2009;36(11):671-674.
2. Who gets HPV. Gardasil [Human Papillomavirus Quadrivalent (Types 6, 11, 16, and 18) Vaccine, Recombinant]. http://www.gardasil.com/hpv/hpv-types/hpv-transmission. Accessed December 14, 2010.
3. Sexually Transmitted Diseases (STDs): Genital HPV Infection—Fact Sheet. Centers for Disease Control and Prevention. http://www.cdc.gov/std/HPV/STDFact-HPV.htm#cause. Updated November 24, 2009. Accessed December 14, 2010.
4. Petäjä T, Keränen H, Karppa T, et al. Immunogenicity
and safety of human papillomavirus (HPV)-16/18 AS04-adjuvanted vaccine in healthy boys aged 10-18 years.
J Adolesc Health. 2009;44(1):33-40.
5. D'Souza G, Agrawal Y, Halpern J, et al. Oral sexual behaviors associated with prevalent oral human papillomavirus infection. J Infect Dis. 2009;199(9):1263-1269.
6. Gillison ML, D'Souza G, Westra W, et al. Distinct risk factor profiles for human papillomavirus type 16-positive and human papillomavirus type 16-negative head and neck cancers. J Natl Cancer Inst. 2008;100(6):407-420.
7. Frequently Asked Questions. Gardasil [Human Papillomavirus Quadrivalent (Types 6, 11, 16, and 18) Vaccine, Recombinant]. Merck Vaccines. https://www.merckvaccines.com/gardasilProductPage_frmst.html. Accessed December 14, 2010.
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