PHILADELPHIA -- Less than a third of women who start out getting the human papillomavirus (HPV) vaccine wind up receiving all three necessary doses, researchers said here.
In a single-center study of almost 10,000 women eligible for vaccination -- those ages 9 to 26 -- only 30.78 percent of the women who started the HPV vaccine regimen actually completed the required three-dose series, Kathleen Tracy of the University of Maryland and colleagues reported at the American Association for Cancer Research Cancer Prevention meeting.
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Tracy told MedPage Today that the findings were generally consistent with a number of other studies based on electronic health record data -- and indicate that many young women are not protected against strains of HPV that could lead to cervical cancer.
Tracy said there were also patterns regarding age and race -- African-American women were more likely to initiate vaccination, but were less likely to follow through. The same was true for women over 18, she added.
"At 18, it's the first time you're making your own medical decisions, organizing your schedule, and making your own appointments," Tracy remarked. "This is the first time there's no parent involved in making those decisions and appointments."
The researchers looked at data from a University of Maryland electronic health record system, which included 9,658 teens and young women who were eligible for HPV vaccination between August 2006 and August 2010.
Among the 2,641 women who started on the HPV vaccine, 39.1 percent received a single dose, 30.1 percent got two doses, and 30.78 percent completed the recommended three-dose regimen.
"Any time you require a patient to get more than one dose, especially when it requires a clinic visit, you're setting up a barrier," Tracy said.
Age was a factor in adherence, as those 18 and older were less likely to take more than a single dose. And black women were less likely than whites to complete the series, the researchers found.
"I think these trends will hold," if applied to the general population, Tracy commented.
A limitation of Tracy's study is that it only looked at data from a single center.
She said the findings suggest the need for improving methods of patient compliance with the dosing schedule. Most HPV vaccines require dosing at the initial visit, one month later, and again at six months.
Tracy and colleagues are in the process of conducting a pilot study for increasing compliance among women ages 18 to 26 by text-messaging them every day for seven days before their vaccine appointments.
Caveats to HPV vaccination include that it only protects against four of the major strains of the virus and others can still cause cervical cancer -- which is why Tracy emphasized the importance of Pap smears even if patients are vaccinated.
"The worst thing is for women to be underprotected and not realize that, and not get Pap smears the way they should be," she said.
This caveat may also influence some women's decisions to not get the vaccine at all, or forgo the full course -- as the cervical cancer screening program in the U.S. has been among its most successful screening programs.
Tracy says it is unclear whether having just one dose of the vaccine offers any protection, although some studies suggest that two doses may be sufficient.
It is also unclear whether immunity to the HPV strains last for a lifetime -- or if women will need HPV booster shots.