Human Papillomavirus Vaccines

Human papillomavirus (HPV) is a nonenveloped, circular, double-stranded DNA virus that infects the basal cells of epithelial mucosa.¹ There are >100 HPV genotypes, with approximately 40 genotypes linked to genital HPV infection.^2,3

HPV types 16, 18, 31, 52, and 58 are most commonly found in women.¹ Although most HPV infections are self-limited and asymptomatic,² persistent oncogenic HPV infection is associated with anogenital cancers (eg, cervical, vaginal, vulvar, penile, and anal), oropharyngeal cancer, and genital warts.^2,4 HPV types 16 and 18 are strongly linked to high-grade cervical disease,^2,5 and are associated with 66% of cervical cancer cases.² HPV types 31, 33, 45, 52, and 58 account for an additional 15% of cervical cancers.^2,4 HPV types 16 and 18 also cause anal, penile, and oropharyngeal cancers in men,⁶ and types 6 and 11 cause >90% of genital warts.^2,6

HPV Vaccines

HPV is the most common sexually transmitted infection in the United States.^1,3,7 The Advisory Committee on Immunization Practices recommends routine HPV vaccination of adolescents aged 11 to 12 years.⁸ The HPV vaccine is most effective when given before the onset of sexual activity,^2,4 and can be given to patients as early as 9 years of age.^9-11 Although prophylactic HPV vaccines were initially designed to prevent cervical cancer, men also benefit from vaccine-induced immunity against diseases such as penile and oropharyngeal cancers.⁶ Currently, there are 3 HPV vaccines approved by the US Food and Drug Administration (FDA): Gardasil (human papillomavirus quadrivalent [types 6, 11, 16, and 18] vaccine, recombinant), Cervarix (human papillomavirus bivalent [types 16 and 18] vaccine, recombinant), and Gardasil 9 (human papillomavirus 9-valent vaccine, recombinant).^9-11 All 3 HPV vaccines are administered intramuscularly as a 3-dose series over a 6-month period; second and third doses are given 1 to 2 and 6 months after the first dose, respectively.^2,9-11 A delay in receipt of the second or third dose does not require that the series be restarted.^4,8 Any available HPV vaccine product may be used to continue or complete the 3-dose series for girls and women; the quadrivalent or 9-valent HPV vaccines may be used to continue or complete the series for boys and men.⁸

Gardasil

Gardasil, approved by the FDA in June 2006,¹² is a recombinant quadrivalent vaccine that was initially indicated for girls and women aged 9 through 26 years, for the prevention of cervical, vulvar, vaginal, and anal cancers caused by HPV types 16 and 18; genital warts associated with HPV types 6 and 11; and preneoplastic lesions caused by HPV types 6, 11, 16, and 18.^1,9 In October 2009, the FDA expanded the indication for use in boys and men aged 9 through 26 years, for the prevention of anal cancer caused by HPV types 16 and 18; genital warts caused by HPV types 6 and 11; and preneoplastic lesions caused by HPV types 6, 11, 16, and 18. Gardasil has been shown to be safe and efficacious, with similar systemic and serious adverse events compared with placebo; however, it had a higher rate of injection site reactions compared with placebo.¹ Note that the second dose of Gardasil is given 2 months after the first dose.⁹

Cervarix

Cervarix, which was approved by the FDA in October 2009,¹³ is a recombinant bivalent vaccine that prevents cervical cancer, and associated precancerous lesions caused by HPV types 16 and 18 in girls and women aged 9 through 25 years.^2,10 Cervarix has been shown to be safe and efficacious, with no reported vaccine-related serious adverse events.¹ Cervarix is not approved for use in boys or men. Note that the second dose of Cervarix is given 1 month after the first dose.¹⁰

Gardasil 9

In December 2014, the FDA approved Gardasil 9.¹⁴ The vaccine covers 9 HPV types,^8,11 and has the potential to prevent approximately 90% of cervical, vulvar, vaginal, and anal cancers.⁶ It prevents cervical, vulvar, vaginal, and anal cancers caused by HPV types 16, 18, 31, 33, 45, 52, and 58; genital warts caused by HPV types 6 and 11; as well as preneoplastic lesions caused by HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58, in girls and women aged 9 through 26 years.^2,11 Gardasil 9 is also approved for prevention of anal cancer caused by HPV types 16, 18, 31, 33, 45, 52, and 58; genital warts caused by HPV types 6 and 11; and precancerous or dysplastic lesions caused by HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58 in boys aged 9 through 15 years.¹¹ Gardasil 9 has been shown to be safe and efficacious, with a safety profile similar to that of Gardasil.¹ Note that, like Gardasil, the second dose of Gardasil 9 is given 2 months after the first dose.¹¹

Low Vaccination Rates

Despite the availability of 3 well-tolerated HPV vaccines, and their established safety and efficacy, vaccination coverage continues to be inadequate, with only approximately 50% of girls aged 13 to 17 years in the United States having received ≥1 vaccine doses, and only 33% having completed the series.⁴

Although HPV vaccination coverage has increased modestly since 2011, national HPV vaccination coverage estimates continue to be low for adolescents.^4,7,15 The reasons for low vaccination rates are multifactorial. There appear to be many missed opportunities for simultaneous administration of HPV vaccines with other routine childhood vaccinations.^3,15 Other reasons for lack of immunizations include parental reluctance, and the misconception of disease risk or adverse reactions from vaccination.³ However, the most surprising source of low vaccination rates stems from providers themselves, with some delaying HPV vaccination until older adolescence.^15-17 Although the immunogenicity of fewer doses is currently unknown,⁸ clinical trials are ongoing to eval­uate alternative dosing schedules, in consideration of reduced-dose HPV vaccination schedules in the United States.^6,15

Conclusion

It is important to emphasize that pre-exposure vaccination is one of the most effective methods for preventing HPV transmission.^1,2,15 Prevention of initial HPV infection is a key factor in reducing the morbidity and mortality associated with HPV.¹ Clinicians should ensure that adolescents of all sexes receive the HPV vaccine when they are aged 11 to 12 years, along with other routine vaccinations. Adolescents and young adults who qualify but have not received any doses should also receive the HPV vaccine.

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References

1. Kash N, Lee MA, Kollipara R, et al. Safety and efficacy data on vaccines and immunization to human papillomavirus. J Clin Med. 2015;4:614-633.
2. Workowski KA, Bolan GA; Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines, 2015. MMWR Recomm Rep. 2015;64(RR-03):1-137.
3. Ackerman LK, Serrano JL. Update on routine childhood and adolescent immunizations. Am Fam Physician. 2015;92:460-468.
4. The American College of Obstetricians and Gynecologists. Committee opinion no. 641: human papillomavirus vaccination. Obstet Gynecol. 2015;126:e38-e43.
5. Radley D, Saah A, Standley M. Persistent infection with human papillomavirus 16 or 18 is strongly linked with high-grade cervical disease. Hum Vacc Immunother. 2015 Sep 18. Epub ahead of print.
6. Brotherton JM, Ogilvie GS. Current status of human papillomavirus vaccination. Curr Opin Oncol. 2015;27:399-404.
7. Newman PA, Lacombe-Duncan A. HPV vaccination for boys and young men: addressing misconceptions and expanding uptake. Inside Patient Care: Retail Clinic Healthcare Solutions. 2015;3:33-35.
8. Petrosky E, Bocchini JA Jr, Hariri S, et al. Use of 9-valent human papillomavirus (HPV) vaccine: updated HPV vaccination recommendations of the Advisory Committee on Immunization Practices. MMWR Morb Mortal Wkly Rep. 2015;64:300-304.
9. Gardasil [package insert]. Whitehouse Station, NJ: Merck & Co, Inc; 2015.
10. Cervarix [package insert]. Research Triangle Park, NC: GlaxoSmithKline; 2015.
11. Gardasil 9 [package insert]. Whitehouse Station, NJ: Merck & Co, Inc; 2015.
12. Baylor NW. June 8, 2006 approval letter – human papillomavirus quadrivalent (types 6, 11, 16, 18) vaccine, recombinant. www.fda.gov/BiologicsBloodVaccines/Vaccines/ApprovedProducts/ucm111283.htm. Updated April 30, 2009. Accessed December 1, 2015.
13. Baylor NW. October 16, 2009 approval letter – Cervarix. www.fda.gov/BiologicsBloodVaccines/Vaccines/ApprovedProducts/ucm186959.htm. Updated April 24, 2012. Accessed December 1, 2015.
14. US Food and Drug Administration. FDA approves Gardasil 9 for prevention of certain cancers caused by five additional types of HPV [news release]. www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm426485.htm. Published December 11, 2014. Accessed October 23, 2015.
15. Reagan-Steiner S, Yankey D, Jeyarajah J, et al. National, regional, state, and selected local area vaccination coverage among adolescents aged 13-17 years—United States, 2014. MMWR Morb Mortal Wkly Rep. 2015;64:784-792.
16. Gilkey MB, Moss JL, Coyne-Beasley T, et al. Physician communication about adolescent vaccination: how is human papillomavirus vaccine different? Prev Med. 2015;77:181-185.
17. Sussman AL, Helitzer D, Bennett A, et al. Catching up with the HPV vaccine: challenges and opportunities in primary care. Ann Fam Med. 2015;13:354-360.