A vaccine against cervical cancer may be on the way -- for boys.
Medical experts in America say it would prevent the passing on of a cancer-causing virus through sex.
Teenage girls in Ireland were offered the jab after a long campaign. But there has been resistance to the vaccine in the US, where a government advisory panel has said it should also be offered to boys.
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 behaviour.
Experts say a key benefit of routinely vaccinating boys could be preventing the spread of the HPV virus to others through sex -- making up for the disappointing vaccination rate in girls.
"It is another milestone in the battle against cancer," said Dr Anne Schuchat, a US Centers for Disease Control and Prevention administrator.
The vaccine has been advised for girls in the US since 2006.
Just 49pc of adolescent girls have had at least the first of the three HPV shots.
Only a third had received all three doses by last year. "Pretty terrible," Dr Schuchat said.
She 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. An estimated 75 to 80pc of men and women are infected with HPV during their life, but most don't develop symptoms or get sick, according to the CDC. Some infections lead to genital warts, cervical cancer and other cancers, including of the head and neck.
The move follows recent studies that show the vaccine prevents anal cancer in males, and may work against a type of throat cancer. A study of gay men found it to be 75pc effective against anal cancer.
Preventing a cancer that's associated with gay men may not be a selling point, said family GP Dr Ranit Mishori.
"Some parents may say, 'Why are you vaccinating my son against anal cancer? He's not gay! He's not ever going to be gay!'" she said.