ATLANTA – A vaccine against cervical cancer hasn’t been all that popular for girls. It may be even a harder sell for boys now that it’s been recommended for them too.

A government advisory panel on Tuesday decided that the vaccine should also be given to boys, in part to help prevent the cancer-causing virus through sex.

Public health officials have tried since 2006 to get parents to have their daughters vaccinated against the human papillomavirus, or HPV, which causes most of the cervical cancer in women.

They have had limited success, hitting a number of hurdles. 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.

Tuesday’s vote by the Advisory Committee on Immunization Practices’ was the first to strongly recommend routine vaccination for boys since the vaccine was first approved for them two years ago. Officials acknowledged the low rate in girls encouraged them to take a new, hard look.

Experts say a key benefit of routinely vaccinating boys could be preventing the spread of the virus to others through sex — making up somewhat for the disappointing vaccination rate in girls. But the recommendation is being framed as an important new measure against cancer in males.

“Today is another milestone in the nation’s battle against cancer,” said Dr. Anne Schuchat, a U.S. Centers for Disease Control and Prevention administrator who oversees the agency’s immunization programs.

Federal health officials usually adopt the panel’s recommendations and ask doctors and patients to follow them.

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. “Pretty terrible,” Schuchat said.

Schuchat 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.

Some conservatives argue the vaccine could promote promiscuous behavior. It has come up in the GOP presidential campaign. Texas Gov. Rick Perry came under attack for a 2007 executive order requiring adolescent girls to get the vaccine (with an opt-out clause). When conservative lawmakers rebelled, he backed down.