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Human papillomavirus (HPV) is commonly found in young people in the United States, with as many as 18% of teenage girls testing positive for HPV.

Teen Topics: Help teens, parents see value of HPV vaccine

July 1, 2009

Teen Topics

Help teens, parents see value of HPV vaccine

By Melanie Gold, DO
Clinical Associate Professor of Pediatrics
University of Pittsburgh School of Medicine
Staff Physician
University of Pittsburgh Student Health Service
and Kaityi Duffy, MPH
Assistant Director of Medical Education
Physicians for Reproductive Choice
New York City

Human papillomavirus (HPV) is commonly found in young people in the United States, with as many as 18% of teenage girls testing positive for HPV.1 Since January 2009, several new studies have emerged that examine genotypic distributions of the virus, the extent of protection afforded by the vaccine, and attitudes of parents and teens toward vaccination.

In the United States, the only Food and Drug Administration-approved vaccine (Gardasil, Merck and Co.; Whitehouse Station, NJ) is quadrivalent and protects against two oncogenic strains (16 and 18) and two nononcogenic strains (6 and 11). Research estimates that the vaccine can prevent up to 70% of cervical cancer cases, but there are limited data available describing HPV genotype distributions in the United States.2 A new study published in the Journal of the National Cancer Institute examines the HPV genotyping of cases of in situ and invasive cervical cancer diagnosed in women aged 18-40 years in New Mexico.3 Results indicate that the most common HPV strains associated with invasive cancers were HPV 16 (56.4%), HPV 18 (13.1%), and HPV 45 (6.1%), and those associated with in situ cancers were HPV 16 (56.3%), HPV 31 (12.6%), and HPV 33 (8.9%).3

Though clearly HPV types 16 and 18 account for most cases of cervical cancer, the quadrivalent vaccine might offer some limited protection against cervical intraepithelial neoplasia (CIN) 1 through 3 and adenocarcinoma in situ (AIS) associated with nonvaccine oncogenic HPV types. Two companion studies were published in February 2009 in the Journal of Infectious Disease analyzing cross-protection by the quadrivalent vaccine against lesions caused by 10 nonvaccine HPV types (31, 33, 35, 39, 45, 51, 52, 56, 58, and 59).4,5 Each was a substudy of Phase 3 clinical trials for the quadrivalent vaccine involving 17,622 participants, ages 16-26 years. The first analysis was a multicenter, double-blind, randomized controlled trial that excluded any participants testing positive for HPV at baseline.4 The second was an intention to treat analysis that included participants regardless of HPV status at baseline.5 Results from the first trial demonstrated a 32.5% reduction in CIN 2-3/AIS associated with the 10 nonvaccine HPV types.4 The intention to treat analysis indicated a statistically significant cross-protective reduction in infection and composite CIN endpoints (mostly due to reductions in CIN1), though greater protection was seen in participants who tested negative for HPV at baseline.5 Although a modest reduction in HPV 31/33/45/52/58-related CIN2 or worse was observed, the estimated reduction was not statistically significant. Authors of both studies urged caution in interpreting the clinical benefits of cross-protection because of possible study limitations.

Though the benefits of the HPV vaccine are clear to the public health community, concern remains about vaccinating children against a sexually transmitted infection. Some research suggests that subclinical genital infections with low- and high-risk HPV types might occur among girls without any history of sexual activity or sexual abuse. A recent study was conducted to determine the prevalence and the natural course of anogenital HPV infections in girls prior to coitarche.6 Researchers took specimens from 114 girls, ages 4 to 15 years, referred for various gynecological problems. Results showed that low-risk HPV was detected in four girls (3.6%) and high-risk HPV in 15 girls (13.6%). Two girls testing positive for HPV DNA had clinically apparent warts. After one year, two girls had persistent high-risk HPV.6

Some parents have expressed concerns that administering the vaccine will increase the likelihood of adolescent sexual risk activity. A study13 published in the April 2009 Journal of Adolescent Health examined the prevalence and predictors of the belief that HPV vaccine will result in increased sexual risk-taking behaviors.7 Three hundred and thirty-two mothers and 360 adolescent girls completed computer-assisted surveys. Results indicated that 26.5% of mothers believed that HPV vaccination would increase the chance of risky sexual behavior among adolescents. Thirty-seven percent of adolescents reported that vaccination would increase risky sex in the general population, but a smaller percentage (8.4%) thought that it would have this effect on themselves personally. These results suggest a need to better counsel about the safety and efficacy of the HPV vaccine.7

Another recent study examined reasons why mothers do or do not vaccinate their daughters (ages 11-17) for HPV.8 During interviews of 52 mothers (19 declining vaccination, 33 accepting), researchers identified several factors underlying mothers' decisions to vaccinate. Lack of knowledge about HPV, age-related concerns, and low perceived risk of infection were commonly cited reasons for declining. Desire to prevent illness, physician recommendation, and a high perceived risk of infection were commonly identified motivating factors. The April 2009 issue of the Journal of Pediatric and Adolescent Gynecology describes a study of 250 adolescents, ages 12-19 years, of whom only 35% intended to be vaccinated.9 However, after reading an information pamphlet about HPV, the percentage that planned to be vaccinated rose to 69%. The pamphlet was positively correlated with adolescents' knowledge, health belief, and belief in who should receive the vaccine.9

Research suggests that in addition to preventing HPV strains 16 and 18, the vaccine might also provide limited cross-protection against nonvaccine oncogenic strains. Regardless of potential benefits of vaccination, there still is some reluctance on the part of parents and adolescents to be vaccinated. Providers might wish to proactively inquire about and address patients' and parents' fears and misconceptions about the HPV vaccine, as well as provide written and oral counseling about the benefits of vaccinating.

References

  1. Centers for Disease Control and Prevention. 2008 National STD Prevention Conference. Nationally Representative CDC Study Finds 1 in 4 Teenage Girls Has a Sexually Transmitted Disease. Press release. Accessed at www.cdc.gov/STDConference/2008/media/release-11march2008.htm.
  2. Harper DM, Franco EL, Wheeler C, et al. Efficacy of a bivalent L1 virus-like particle vaccine in prevention of infection with human papillomavirus types 16 and 18 in young women: A randomised controlled trial. Lancet 2004; 364:1,757-1,765.
  3. Wheeler CM, Hunt WC, Joste NE, et al. Human papillomavirus genotype distributions: Implications for vaccination and cancer screening in the United States. J Natl Cancer Inst 2009; 101:475-487.
  4. Brown DR, Kjaer SK, Sigurdsson K, et al. The impact of quadrivalent human papillomavirus (HPV; types 6, 11, 16, and 18) L1 virus-like particle vaccine on infection and disease due to oncogenic nonvaccine HPV types in generally HPV-naive women aged 16-26 years. J Infect Dis 2009; 199:926-935.
  5. Wheeler CM, Kjaer SK, Sigurdsson K, et al. The impact of quadrivalent human papillomavirus (HPV; types 6, 11, 16, and 18) L1 virus-like particle vaccine on infection and disease due to oncogenic nonvaccine HPV types in sexually active women aged 16-26 years. J Infect Dis 2009; 199:936-944.
  6. Doerfler D, Bernhaus A, Kottmel A, et al. Human papilloma virus infection prior to coitarche. Am J Obstet Gynecol 2009; 200:487.e1-487.e5.
  7. Marlow LA, Forster AS, Wardle J, et al. Mothers' and adolescents' beliefs about risk compensation following HPV vaccination. J Adolesc Heath 2009; 44:446-451.
  8. Dempsey AF, Abraham LM, Dalton V, et al. Understanding the reasons why mothers do or do not have their adolescent daughters vaccinated against human papillomavirus. Ann Epidemiol 2009. Doi: 10.1016/j.annepidem.2009.03.011.
  9. Chan SS, Yan Ng BH, Lo WK, et al. Adolescent girls' attitudes on human papillomavirus vaccination. J Pediatr Adolesc Gynecol 2009; 22:85-90.