WASHINGTON – The prevalence of human papillomavirus (HPV) types 16 and 18 has significantly decreased, but only among vaccinated women; national data show no evidence that the vaccine targeting them has conferred herd immunity or encouraged a shift toward lower-risk types.
From 2003, before the vaccine was introduced, to 2012, the prevalence of HPV 16 and 18 fell from 10% to about 4% in completely vaccinated women, Dr. Christopher Tarney said at the annual meeting of the American College of Obstetricians and Gynecologists. The prevalence among unvaccinated women, however, was virtually unchanged.
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“Our study didn’t demonstrate crossprotection, type replacement, or herd immunity,” said Dr. Tarney of the Womack Army Medical Center, Ft. Bragg, N.C. “This is in contrast to some global data” that have recently shown such positive changes were linked to high HPV vaccine coverage in Scotland and Australia.
The lack of these findings in the United States probably has to do with the low rate of vaccine acceptance, Dr. Tarney said. Although 60% of eligible girls got at least one dose of the vaccine in 2014, only about 40% received the entire series.
Dr. Tarney compared data from the 2003 National Health and Nutrition Examination Survey (NHANES) for women 18-29 years old, with NHANES waves in 2007-2008, 2009-2010, and 2011-2012. He looked at the prevalence of high-risk HPV serotypes, and at the specific prevalence of HPV 16 and 18, which are specifically targeted in the vaccine. The study comprised 1,628 women who had submitted self-collected vaginal swabs for HPV analysis. The group was representative of more than 21 million U.S. women, Dr. Tarney said.
The prevalence of HPV 16 and 18 decreased significantly among vaccinated women, from 10% in 2003 to 4% in 2012. Even women who didn’t complete the series reaped some benefit from it. Among those who had at least one immunization, all high-risk HPV decreased from 67% in 2007-2008 to 41% in 2012.
Despite the vaccine’s effectiveness, it is not exerting crossprotection against other high-risk types, Dr. Tarney said, nor is there evidence of herd immunity. Among women who did not receive the vaccine, high-risk HPV prevalence was unchanged at about 49% in 2007-2008 and 51% in 2011-2012.
He expressed frustration that the vaccine has not been more widely adopted.
“During this postvaccine era, over 16 million eligible females didn’t get it. As women’s health care physicians, we must reduce missed clinical opportunities to administer this vaccine. We must strive to maximize access to it and increase support for it,” Dr. Tarney said. “We have a great opportunity to have a profound impact on the prevention of cervical cancer, but only when we can drastically increase the vaccination rates will we see these vaccines begin to contribute to the eradication of cervical cancer in the U.S.”
He reported having no relevant financial disclosures.