Many young men who report having sex with other young men have the human papillomavirus (HPV) that can lead to genital warts and anal cancer, according to a new study from Australia.

The results, based on men as young as 16, suggest that vaccination could help lower infection rates in this population. The findings also strengthen the U.S. recommendation that all children ages 11 and 12 years old receive the series of shots to prevent HPV, said one expert.

“It suggests that gender-neutral vaccination is important,” Noel Brewer told Reuters Health by phone. “Parents should get HPV vaccination for their children whether they’re boys or girls.”

Brewer, who wrote an editorial about the new study in The Lancent Infectious Diseases, is an expert on the HPV vaccine at the University of North Carolina, Chapel Hill.

HPV vaccination is most beneficial when given to people before they are sexually active, according to the U.S. National Cancer Institute. Brewer said it would be nearly impossible to target only high-risk boys and girls for vaccination.

“Most young people don’t know they’re gay yet,” he said. “If they do, they likely haven’t told their parents.”

Researchers already knew that HPV infections are common among gay and bisexual men, but less was known about infection rates in younger age groups. Data on adolescent infection rates are needed to create effective vaccination programs, the researchers write.

For the new study, Huachun Zou at the Melbourne School of Public Health and colleagues recruited 200 adolescent males, ages 16 to 20, who were attracted to other males. The participants were never vaccinated against HPV and had few sexual encounters.

At four points over one year, the researchers collected three swabs from each participant’s penis, mouth and anal canal to test for HPV.

Over that period, they found 48 definite anal HPV infections, 10 penile infections and no mouth infections.

The researchers say the infection rates would mean that among 100 gay and bisexual males in that age range, there would be 57 new anal infections every year. Vaccination could protect against 33 of those 57 infections.

Similarly, there would be 12 new penile HPV infections every year among 100 gay and bisexual males in that age group. Vaccination could protect against five of those infections.

Linking their data to those of another study, the researchers estimated there is a 50 percent chance of HPV passing from a man’s penis to the anal canal of another. The risk of HPV going from anal canal to penis was lower, however.

The high incidence of HPV infections and the high probability of the virus being transmitted suggests a high vaccination rate is needed among young gay and bisexual men to achieve the same reduction in infections, genital warts and precancerous growths found among heterosexual individuals, write Zou - now at the University of New South Wales in Sydney - and colleagues.

Brewer, who has worked with companies that produce the HPV vaccines, pointed to another study that found the percentage of young Australians diagnosed with genital warts fell from about 12 percent in 2007, when the vaccines were made available for females, to about 2 percent to 3 percent in 2011.

Meanwhile, he said, there has been no significant change in genital wart incidence among gay and bisexual men, who would not benefit as much if only women are vaccinated.

“Gender neutral vaccination would have a big impact on reducing cancer and genital warts,” Brewer said.

Australia now offers the HPV vaccines through a school-based program to boys and girls ages 12 to 13.

Two vaccines against HPV are offered in the U.S. Cervarix, from GlaxoSmithKline, is approved for females. Gardasil, which is produced by Merck, is approved for both males and females.

The U.S. Centers for Disease Control and Prevention recommends that all children receive the HPV vaccine between ages 11 and 12. The agency also recommends the vaccine through age 26 for women and for men who have sex with men. For men who have sex with women, the vaccine is recommended through age 21 years.

“The vaccine may not have as much to offer you if you're older,” Brewer said. Still, gay and bisexual men can consider the vaccine, which is administered through three shots over six months.