Studies of Gardasil show that the vaccine provokes an even stronger immune response in boys than in girls, which implies that the vaccine will also prevent HPV infections, Blumberg says. But they have yet to show that boys are protected from HPV infection at satisfactory rates. Researchers are also examining whether the vaccine reduces cases of anal cancer in gay men.
There is "no guarantee" an HPV vaccine will work in men, Broker says, because the skin cells infected by the virus differ greatly in men and women.
Some people aren't waiting for the results of those studies. High-risk men, such as gay and bisexual men, are reportedly requesting and receiving Gardasil vaccination from their physicians, Blumberg says.
Moreover, he says, "I've had nurses tell me they made sure their 15-year-old son was vaccinated because they wanted to decrease the chance of their future daughter-in-law having cervical cancer. They felt strongly about it."
Historically, vaccination programs have had the most impact when they are gender-neutral.
For example, when the rubella vaccine was introduced in the late 1960s, it was recommended initially for women of child-bearing age because -- while anyone can become infected -- rubella in pregnant women causes serious birth defects.
However, the campaign was only partially effective and eradication of the disease was only achieved after the vaccine was recommended to both boys and girls.
GlaxoSmithKline plans to seek Food and Drug Administration approval next month for its HPV vaccine for girls and women, Cervarix.
And legislation requiring California girls to complete HPV vaccination before entering seventh grade was introduced last week by Assemblyman Edward Hernandez (D-West Covina). Another bill was proposed that would require health insurers to cover the cost of the vaccinations.
Lawmakers in as many as 20 other states have introduced similar proposals. But mandatory vaccination of school-age girls has generated controversy because some parents believe their daughters will not be exposed to the virus or that having the vaccination might encourage sexual activity.
Others object to mandating vaccination for something that is not easily transmitted (unlike chickenpox or measles) and because the shots are costly, about $360 for the series.
"Some people resent the fact that a mandate is targeting just one gender," says Blumberg. "It does give the appearance of being unfair. We don't have any other vaccine mandates that are gender specific."