Nick Mulcahy

November 10, 2010

November 10, 2010 (Philadelphia, Pennsylvania) — Nearly 70% of young women and girls who received a human papillomavirus (HPV) vaccination at a medical center in Baltimore, Maryland, did not complete the recommended 3-dose regimen, according to a new study.

Of the 2641 females (aged 9 to 26 years) who started HPV vaccination from 2006 to 2010, 39.1% received a single dose, 30.1% received 2 doses, but only 30.78% completed the recommended 3-dose regimen.

"If we are going to offer a vaccine, we need to know who's getting it and who's getting the full course so we know who's protected and who's not," said the study's lead author, J. Kathleen Tracy, PhD, assistant professor of epidemiology and public health at the University of Maryland School of Medicine in Baltimore.

Not completing a full course of the vaccine results in underprotection, said Dr. Tracy in an interview with Medscape Medical News. She presents the results of her study today here at the Ninth Annual American Association for Cancer Research International Conference on Frontiers in Cancer Prevention Research.

Dr. Tracy said that she did not anticipate that 18 to 26 year olds would be the age group least likely to complete all 3 doses of the regimen.

"Given all of the marketing and attention about the HPV vaccine, I was surprised by the lack of follow-through among young women," she said.

"It's probably the first time they are managing their own medical care," said Dr. Tracy about the young adults. The girls and teens in the study, on the other hand, were likely shepherded through the process by parents or guardians, and were therefore more likely to complete the process, she suggested.

Dr. Tracy and her team are now at work on a follow-up pilot study of young women to learn if text messaging will increase their rates of completing the 3-dose vaccination process.

Dr. Tracy said that blacks in the study were significantly less likely to complete the full course than whites (P = .001).

Baltimore Is Not Alone

During the study period, 9658 girls and young women were seen at the University of Maryland Medical Center for gynecological problems in either the gynecology or family medicine departments, and were eligible for HPV vaccination.

Out of this pool of females, 2641 (27.3%) actually started the HPV vaccination regimen; about two thirds of the participating females were black. Dr. Tracy said that HPV vaccination is routinely offered to females in the 9 to 26 age range at the medical center.

This rate of participation in Baltimore is not unique, said another expert. "Unfortunately that has been our experience in Atlanta as well," said Kevin Ault, MD, from Emory University in Atlanta, Georgia.

Dr. Ault told Medscape Medical News that "the idea of adolescent vaccination is fairly new;" HPV vaccination was only started in 2005.

How can participation increase?

Dr. Ault, who is an associate professor of obstetrics and gynecology, points to his fellow physicians. "Most studies indicate that physician recommendation is the strongest factor predicting vaccination for any vaccine, so pediatricians and other doctors who see adolescents need to be familiar with HPV and its role in causing cervical cancer, abnormal Pap smears, and premalignant cervical disease," he said.

In terms of a national picture in the United States, a study on the uptake of HPV vaccination earlier this year from the Centers for Disease Control and Prevention indicated that 25% of adolescents 13 to 17 years of age reported receiving at least 1 dose of the quadrivalent HPV vaccine. However, as with the current study, a minority of these teens completed the full course — only 11% reported receiving all 3 doses.

Dr. Tracy believes that the 27.3% uptake of vaccination at her medical center is "probably an overestimation of the initial uptake of the vaccine." The overestimation, she said, stems from the fact that the study subjects all had a gynecological compliant during their office visit, and thus had a focus on their reproductive organs. She and her colleagues are going to do another study to test that hypothesis.

"We are going to go back and look at all patient visits among females aged 9 to 26 and evaluate HPV vaccination participation among them," she said. "The participation rate will likely be considerably lower."

Teens and HPV Infection

With regard to the benefits of vaccination, the uptake of the vaccines, and the related influence of marketing, there has been a great deal of controversy, as previously reported by Medscape Medical News.

HPV is the most common sexually transmitted disease among adolescent girls in the United States, with 29.5% of sexually active 14 to 19 year olds infected at any given time, according to press materials from the University of Maryland.

However, as Dr. Tracy explains, the "vast majority" of these girls will clear the infection on their own; only "about 10%" will develop persistent infections.

About 70% of cervical cancers are linked to initial infection with HPV 16 or 18, which both commercially available vaccines protect against, said Dr. Tracy. "You can't stop getting your Pap smears as part of cervical cancer prevention because other HPV strains can cause cervical cancer and are not covered by vaccination."

HPV vaccination is "one of many strategies for preventing cervical cancer, and families and women need to evaluate which strategy is most comfortable for them," advised Dr. Tracy.

The researchers have disclosed no relevant financial relationships.

Ninth Annual American Association for Cancer Research (AACR) International Conference on Frontiers in Cancer Prevention Research: Abstract PR-11. Presented November 10, 2010.

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