Vaccines for the human papillomavirus (HPV) might not be just for girls anymore. A medical advisory panel for the U.S. Food and Drug Administration (FDA) voted today that the use of Gardasil to prevent HPV, a sexually transmitted disease, in males ages nine to 26 would be both safe and effective.

Each year about six million people in the U.S. get HPV, which can cause genital warts and cancer in both men and women. The resulting cancer (cervical in women) is diagnosed in about 11,000 women each year, according to the American Cancer Society. Males can also acquire cancer from HPV—anal or penile—which is diagnosed in about 2,100 and 1,300 U.S. men, respectively. Prevention of genital warts would be Gardasil's primary target for use in males. Experts have also noted that staving off the virus in males could help protect women by preventing further spread.

The panel's decision could open up a large market for Gardasil maker, Merck, which has been approved to market the vaccine in the U.S. to females ages nine to 26 since 2006 and has distributed more than 50 million doses globally. A market analyst told Forbes, however, that sales of Gardasil to males will likely be remain below 20 percent of the vaccine's total. But even that nudge could bring in upward of an additional $300 million a year, said Seamus Fernandez, an analyst at health care investment company Leerink Swan.

Despite the male-market bump, Gardasil will likely face new competition on the female side. An FDA advisory panel also voted today that Cervarix—another HPV vaccine, made by GlaxoSmithKline PLC—is safe and prevents the infection in girls.

The FDA will take all panel recommendations into consideration but is not bound to follow their advice.

Out of more than 100 strains of HPV, two types (six and 11) are responsible for 90 percent of genital wart cases, and two others (16 and 18) are responsible for 70 percent of cases of cervical cancer. Gardasil protects against all four, and Cervarix protects against 16 and 18—making it unlikely to be marketed to males.

Image courtesy of Wikimedia Commons/Eugene Peretz