Human papillomavirus, or HPV, is sexually transmitted, making the vaccination very controversial. The government already recommends an HPV vaccine for girls, but it hasn't been popular.
A government advisory panel on Tuesday decided that the vaccine should be given to boys as young as 11 years old. Federal health officials usually adopt the panel's recommendations and ask doctors and patients to follow them.
Some parents distrust the safety of vaccines, especially newer products. Others don't want to think about their daughters having sex one day, or worry that the vaccine essentially promotes promiscuous behavior.
Supporters of the move said the bottom line is that it's going to save lives.
Phil Keane said one day he noticed a lump on his neck, and it turned out to be late-stage throat cancer. The cause was HPV.
"You don't want them waking up in 20 or 30 years and finding out they have stage-four throat cancer. That's where I am now," said Keane.
Keane's case is one of more than 8,500 HPV-positive head and neck cancers this year. The numbers have increased dramatically over the last decade.
"These vaccines are very important. They're as important as polio and rubella and mumps and all the other vaccines that young kids receive," said Dr. Eric Genden of the Mt. Sinai School of Medicine.
ABC News health editor Dr. Rich Besser agrees.
"It was clear to me there was benefit to boys. This summer, I vaccinated my sons," said Besser.
But Besser admits that many parents are not comfortable with the idea.
"This vaccine forces parents, when they have an 11-year-old or 12-year-old, to think about their children's future sex life, and that's a hard conversation for a lot of parents to have," said Besser.
The vaccine has been advised for girls since 2006. Just 49 percent of adolescent girls have gotten at least the first of the three HPV shots. Only a third had gotten all three doses by last year.
Dr. Anne Schuchat, a U.S. Centers for Disease Control and Prevention administrator, attributed the low rates for girls to confusion or misunderstanding by parents that they can wait until their daughter becomes sexually active. It works best if the shots are given before a girl or boy begins having sex.
An estimated 75 to 80 percent of men and women are infected with HPV during their life, but most don't develop symptoms or get sick, according to the CDC. Some infections lead to genital warts, cervical cancer and other cancers.
The Associated Press contributed to this report.