Although HPV causes 18,000 cancers in women each year, it also causes 8,000 cancers in men, the CDC calculates. To get the figures, CDC researchers analyzed data collected from 2004 to 2008 in two large cancer registries.

HPV, human papillomavirus, is the cause of nearly all cervical cancers. But that's obviously not the only cancer caused by this sexually transmitted virus.

HPV also causes about two-thirds of mouth/throat (oropharyngeal) cancers, 93% of anal cancers, and more than a third of penile cancers. Men are four times more likely than women to get HPV mouth/throat cancer, while women are more likely than men to get HPV anal cancer.

Clearly, HPV is not just a female problem. Yet it was only last year that one of the two FDA-approved HPV vaccines was recommended for teen boys. Gardasil was recommended for girls in 2006; Cervarix was recommended for girls in 2009.

"HPV vaccines are important prevention tools to reduce the incidence of non-cervical cancers," the CDC notes in a report in the April 20 issue of Morbidity and Mortality Weekly Report. "Transmission of HPV also can be reduced through condom use and limiting the number of sexual partners."

HPV vaccines are most effective when given before people become sexually active. Yet in 2010, less than a third of teen girls had received all three doses of HPV vaccines. Numbers aren't yet available for boys.

The slow uptake of the vaccine by teen girls is in stark contrast to the contribution HPV makes to women's cancer risk. Taken together, HPV cancers are more common than ovarian cancers, and nearly as common as melanoma skin cancers in women.

Among men, HPV cancers are about as common as invasive brain cancers.

HPV Prevention

HPV is an extremely common sexually transmitted infection. At least half of sexually active people get HPV at some time during their lives. At any given time, more than 20 million Americans carry the virus.

Each HPV infection usually clears after a year or two. But that doesn't always happen. Those HPV infections that persist can lead to the development of cancers.

Although condom use and limiting the number of one's sex partners reduce HPV spread, vaccination -- before a person becomes sexually active -- is the surest way to prevent infection.

The Cervarix HPV vaccine protects against the two HPV strains most likely to cause cervical cancer. The Gardasil HPV vaccine protects against these and two other HPV strains.

Routine vaccination with three doses of Cervarix or Gardasil is recommended for girls aged 11 or 12. Routine vaccination with three doses of Gardasil is recommended for boys aged 11 or 12. Catch-up vaccination is recommended for females through age 26 and for males through age 21.