What's the best way to protect teenage girls from sexually transmitted diseases? Some doctors say the answer is to vaccinate boys.
More than 65 million Americans -- that's one in five -- carry a sexually transmitted disease. The most common one -- the human papilloma virus, or HPV -- affects more than half of sexually active Americans at some point, according to the federal government.
Since 2007, health officials have recommended that adolescent girls get vaccinated against HPV because it can lead to cervical cancer later in life.
Now, they're also suggesting the vaccine for boys to prevent genital warts and anal cancer, rare symptoms of HPV. But for some doctors, vaccinating boys is also a favored new strategy in preventing the spread of the virus to girls.
Dr. Sameena Evers, a physician at Dilworth Pediatrics, encourages boys to get vaccinated against HPV "so that girls don't get it." This kind of practice is called "herd immunity," or vaccinating one segment of the population to protect another.
Officials say that along with Pap smears, vaccinating girls is the most effective way to prevent cervical cancer.
They say it's as important for girls as vaccinating against illnesses like tetanus, meningitis and the flu. The series of three shots cost about $400 or more but is covered by Medicaid and most private insurance programs.
Since the approval of the vaccine for boys in 2009, health officials have debated whether vaccinating boys for girls' sake is an effective way to control cervical cancer. In part, there are questions about how long the vaccine stays active in boys' bodies.
The federal government recommends the vaccine for boys, too, but it's considered less urgent. It's optional for doctors to tell boys and their parents about it.
But many doctors are recommending it to both boys and girls with the same urgency. Every year, cervical cancer leads to about 4,000 deaths in the United States. (By comparison, breast cancer kills 10 times as many women.)
The correlation between cervical cancer and some types of HPV is clear: the primary cause of the cancer in women is HPV. One out of 10,000 women who contract HPV end up with cervical cancer.
Most infections clear up on their own within a couple of years and don't develop into cervical cancer. Nonetheless, some 35 million doses of Gardasil have been distributed in the U.S.
Some attribute the gender difference to heavy advertising for Gardasil by Merck, the manufacturer, that targeted middle and high school-aged girls and their parents. The pharmaceutical company hasn't done that for boys.
Health experts say patients are learning about Gardasil mostly from their doctors.
Dr. Preeti Matkins, the medical director of the Teen Health Connection in Charlotte, N.C., encourages her male patients to get the Gardasil shots. And when Gardasil was approved for boys, she sent her 14-year-old son to get his shots.
She said that discussions about Gardasil make some parents uncomfortable, especially when it comes to the teenage children they believe won't become sexually active for a long time. Sometimes, doctors themselves are uncomfortable discussing it with parents, she said.
And then there's the parental fear that giving their child the vaccine encourages sexual activity, she said.
Religious groups such as the Family Research Council have advocated strongly against the Gardasil vaccine for these reasons. They emphasize abstinence over immunization.
"Religion is often used as reason for non-vaccinators " Matkins said.
Nationally, while teens and young adults represent only a quarter of the sexually active population, they account for half of the new STD cases every year.
Not all doctors are on board with use of the Gardasil vaccine for either gender. Some have criticized the speed with which the drug was approved. They say Pap smears are a highly effective tool for detecting cervical cancer and that the vaccine is just another layer of cost.
Once a consultant for Merck, Dr. Diane Harper is one of Gardasil's most outspoken critics. One of the biggest problems is "the way it's been marketed and sold and crammed down people's throats so that companies have a profitable bottom line for making their investment into the research," said Harper, a professor of medicine at the University of Missouri.
She is convinced that if Gardasil vaccine for boys becomes a higher priority, "Merck will hit the advertising market hard for boys."
And parents will start hearing about it a lot more.