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With controversy continuing to simmer in some quarters over the human papillomavirus (HPV) vaccine, three new studies exploring who benefits most from its use and the factors impacting its adoption may help to foster increased vaccination rates.

The Advisory Committee on Immunization Practices (ACIP) recommended routine vaccination of females aged 11 to 12 years and noted that the quadrivalent HPV vaccine is licensed for use in females between 9 and 26 years old (MMWR. March 23, 2007;56[RRO2]:1-24). The first study reinforces the value of adhering to these recommendations, finding that administration of HPV vaccine may reduce the risk of a range of genital diseases among adolescents and young women.

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The study (from the Feb 5, 2010 Journal of the National Cancer Institute. [Epub ahead of print]) looked at 17,622 women aged 15 to 26 years who were enrolled in one of two randomized placebo-controlled efficacy trials for the HPV6/11/16/18 vaccine. Outcomes included cervical intraepithelial neoplasia (CIN, a precursor of cervical cancer), external anogenital and vaginal lesions, Pap test abnormalities, and procedures such as colpscopy and definitive therapy or excision of lesions. A limitation of the study was that only 14 of the 40 HPV types that infect the genital tract were assessed.

Among women who were uninfected, the study revealed that vaccination was up to 100% effective in reducing the risk of HPV16/18-related high-grade cervical, vulvar, and vaginal lesions and the risk of HPV6/11- related genital warts. For the group representing the general population, researchers reported that vaccination reduced the risk of any lesion, genital warts, Pap test abnormalities, and definitive therapy, irrespective of HPV type.

The second study, in the Feb 15, 2010 Journal of the National Cancer Institute (Epub ahead of print), reinforced the notion that older women may not benefit from HPV vaccinations or frequent HPV screenings.

The researchers examined whether women’s age and the duration of carcinogenic HPV infections influenced subsequent persistence of infection and the risk of CIN grade 2 (CIN 2) or worse disease. Ana Rodriquez, MD, and colleagues screened more than 9,000 women in Costa Rica aged 18 to 97 years. Participants with CIN 2 or worse disease at enrollment were treated and not followed any further for the duration of the study. Those at low-risk of CIN 2 or worse were rescreened at 5 to 7 years, and higher-risk participants and subsets of low-risk women and initially sexually inactive women were rescreened either annually or semi-annually for up to 7 years.

The rate of new infections preventable by vaccination declined with age, the researchers found. The team also reported that the rate of newly detected carcinogenic HPV infections decreased with increasing age and ranged from 35% in women 18 to 25 years of age to 13.5% in women ≥42 years old.

Finally, other than the recommendations of medical experts, what factors can impact a parent’s decision on whether to have their child vaccinated for HPV?

According to a study published in Cancer Epidemiology, Biomarkers & Prevention (2010;19[2]:319- 326), it could involve something as unusual as whether or not that parent is a smoker. Researcher Carolyn Fang, PhD, an associate professor in the Cancer Prevention and Control Program at Fox Chase Cancer Center, used information from a 2007 survey from more than 1,300 parents or guardians of female children or adolescents ≤18 years old to examine the multiple behavioral correlates of HPV vaccine acceptability.

Dr Fang found that approximately 18% of the participants would not let their daughters receive the HPV vaccine, about 25% were undecided, and approximately 58% reported that they would have their daughters vaccinated. Data collected showed that the parents who were more accepting of the vaccine were either current or former smokers, engaged in health-promoting activities within the past month, or had not used alternative, complementary, or unconventional therapies within the past year. What is more, the parents who were more likely to have their daughters vaccinated believed that cancer can be cured if caught early.

“Saying that parents would or would not vaccinate their daughters does not necessarily translate into action or lack of action for vaccination. There may be unanticipated barriers when parents attempt to get their daughters vaccinated, such as cost or access to health care, said Sally Vernon, PhD. Dr Vernon is director of the Division of Health Promotion and Behavioral Sciences at the University of Texas-Houston School of Public Health and editor of the journal in which the study was published. ONA