New research indicates that genital warts started declining in Sweden after the country began offering subsidized human papillomavirus vaccinations to teenage girls in 2007. Rates of the STD dropped by 17 percent among women ages 15-25 from 2006 to 2010, although the rates in men did not change. Genital warts are caused by HPV, and US health authorities recommend the shots for all preteens.
By e-mail, study researcher Amy Leval of the Karolinska Institutet in Stockholm said the findings are “in all likelihood” a sign the vaccine is working. She also said they suggest that not enough women were vaccinated to protect men indirectly - a phenomenon called herd immunity.
“It’s exactly what we would like to see,” said Dr. Michael Brady, a pediatric infectious-diseases expert at Nationwide Children’s Hospital in Columbus, Ohio, who has no ties to the research. “But it is a little early to suggest that we know this is a vaccine response.” Better education or increased media attention might have also affected the decline, he explained.
Leval said her work is the first to use population data from an entire country to estimate genital wart infections. Two national registries were linked, one on prescription drug use and one on hospital visits, to get treatment estimates. The registries did not include people who got non-drug treatments in private practices. Women were most at risk for infection around age 20, whereas the rate peaked slightly later in men.
After 2007, when HPV vaccinations began, 27 percent of females ages 17-19 were fully vaccinated and the rate of new infections in this age group dropped by a quarter. This year Sweden replaced its on-demand vaccination strategy with “a school-based and catch-up vaccination program,” Leval said.
[PNU editor’s note: The study, “Incidence of Genital Warts in Sweden Before and After Quadrivalent Human Papillomavirus Vaccine Availability,” was published in the Journal of Infectious Diseases (2012;doi:10.1093/infdis/jis405).]
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