Cases of HPV in young women and girls are falling, which should lead to fewer cancer cases in the US in the coming years. CDC researchers, who began recommending the vaccine for women and girls in 2006, say the results of a new study are "exactly what we would expect." After the HPV vaccine became available, infection rates fell 64% to 4.3% among girls 14 to 19 and dropped 34% to 12.1% among women 20 to 24. Rates of HPV—the most common STI in the US—among women 25 and older did not drop, though this age group is far less likely to be vaccinated, per the New York Times and Guardian. The rate among sexually active females 24 and under who were vaccinated was just 2.1% from 2009 to 2012, while the rate among those who weren't vaccinated was significantly higher at 16.9%, reports USA Today. One doctor calls the study "incredibly exciting."
"The vaccine is more effective than we thought," says Debbie Saslow of the American Cancer Society. "It means there's going to be a whole lot less disease" related to HPV. Cases of genital warts and pre-cancers for women in their 20s will begin dropping soon, followed by cases of cervical, vaginal, anal, and throat cancers in a decade or so, she adds. "But we would see greater impact with greater vaccine coverage," the study's lead author says. By 2012, researchers found just 51% of teen girls and 33% of women under 24 had received at least one of the three doses of the vaccine. Saslow says it isn't as strongly recommended by doctors as other vaccines, but the Times notes this study will likely "serve as a welcome energizer in the tumultuous struggle to encourage HPV vaccination." Later studies will focus on the vaccine's effect on young men and boys. (Most healthy Americans have HPV.)