A doctor administers the HPV vaccine. (Getty)
Elizabeth Weise, USA TODAY
A vaccine against the human papillomavirus has decreased the incidence of the cancer-causing virus among teenage girls by 56%, despite being available since only 2006, a study released Wednesday finds.
"Today we have really good news," said Thomas Frieden, director of the Centers for Disease Control and Prevention. "These are striking results."
The human papillomavirus (HPV), which is sexually transmitted, can cause genital warts, cervical cancer and throat cancer. The CDC recommends that all girls get the vaccine at age 11 or 12 to protect them against cancers that can appear 20 to 40 years later.
About 79 million Americans, most in their late teens and early 20s, are infected with HPV. Each year, about 14 million people become newly infected. About 19,000 women in the United States get cancer caused by HPV each year, cervical cancer being the most common.
Men can also get cancer from HPV. Each year about 8,000 men get these cancers, mostly in the throat. The CDC began recommending in 2011 that boys over 11 also get the vaccine.
The vaccine is also recommended for older teens and young adults who were not vaccinated when they were younger.
The study was published in the June issue of The Journal of Infectious Diseases.
"This is an anti-cancer vaccine," Frieden said. "We owe it to the next generation to protect them against cervical cancer."
Frieden expressed concern that only one-third of girls 13-17 have gotten a full course of three HPV vaccine injections.
"Our low vaccination rates represent 50,000 preventable tragedies: 50,000 girls alive today will develop cervical cancer over their lifetime that would have been prevented if we reached 80% vaccination rates. For every year we delay in doing so, another 4,400 girls will develop cervical cancer in their lifetimes."
The study used data from the National Health and Nutrition Examination Survey to compare the proportion of girls and women 14-59 who had certain types of HPV before and after the vaccination program began. Rates in young women infected with the virus dropped 56% from the period 2003-06 to 2007-10.
Doctors aren't sure why the decline is so great given that only 46% of young women have received at least one dose and only 32% have received all three. It could be what's called herd immunity, in which the vaccinated women lower the overall amount of the virus in the population, thus lowering infection rates for everyone, said Lauri Markowitz, lead author of the study. "This decline is encouraging, given the substantial health and economic burden of HPV-associated disease," she said.
The findings are welcome, said Debbie Saslow, director of breast and gynecologic cancer with the American Cancer Society in Atlanta. "What's surprising is just how much HPV infection has gone down in so little time."
The United States is far behind many other countries in how many teens get the vaccine. In countries such as Australia, where 70% to 80% of teenage girls are vaccinated against the HPV virus, health officials are already seeing a significant decline in genital warts in young women as well as a decline in abnormal Pap smears, which are an early precursor to cancer, Saslow said.
Some parents have balked at having their children and teens vaccinated for a sexually transmitted disease out of concern that it could encourage sexual activity. Frieden said the vaccination is meant to protect them when they become adults.
"We vaccinate well before people are exposed to an infection," he said. "We vaccinate for measles, for example, early in childhood or infancy because that's well before a child may get exposed. Similarly, we want to vaccinate children well before they may get exposed."
Another reason cancer researchers believe the vaccine is not used as broadly here as elsewhere is Americans' discomfort with sex. "Some doctors don't go out of the way to recommend it because they want to avoid talking about sex or they think the parents want to avoid talking about sex," Saslow said.
The American Cancer Society and the CDC are trying to change that thinking. "It's not called the 'cervical cancer prevention vaccine.' Maybe it should be," she said.