For years, many more girls than boys have gotten the vaccine against HPV. Now drugmaker Merck, headquartered in New Jersey, has a vaccine that gives teen boys and young men more options for protection.

The human papillomavirus is the most common sexually transmitted infection. In the vast majority of people, the virus clears the body but the infection can cause certain cancers later in life in a small percentage of others.

Federal health officials suggest that all kids be vaccinated beginning at 11 or 12. If older teens and young adults miss their routine shots as adolescents, they can be vaccinated up until age 26, according to the Centers for Disease Control and Prevention.

Merck just announced that its vaccine against human papillomavirus is now also approved for older boys and young men.

The first HPV vaccine entered the market nearly a decade ago, introduced just for girls, and many Americans heard about it through a large advertising campaign. Soon after, political fights broke out when some public health advocates wanted to make the immunization mandatory for school admission.

"The awareness of the vaccine for girls was pretty well known," said Amy Leader, a public health researcher at Thomas Jefferson University.

"Either you were following the news or you saw an ad, or something like that. For boys, for males, it was just sort of a quiet roll out," she said. "Part of it is just has to do with parents' knowledge and understanding that the vaccine is now approved for males."

A strong recommendation from a doctor is often the reason families decide to get the vaccine for a child, Leader said.

"Some families don't quite understand why the vaccine would be recommended for boys, and it takes a conversation to explain how the cancers prevented by the vaccine are also very relevant to boys," said Alex Fiks, a primary care pediatrician at the Children's Hospital of Philadelphia.

A vaccine in adolescence can protect males from genital warts and some cancers, caused by certain types of HPV.

To be fully protected, kids need the three-dose immunization.

"So to get children vaccinated they have to be back in the office multiple times, so reminders to families that keep them coming back on schedule to receive the vaccine are really important," Fiks said.

Health officials want pediatricians and other providers to offer the HPV vaccine in the same way C and on the same day — that they offer other adolescent immunizations.

"And CDC is adopting that," Leader said. "So 'same way' — we are going to talk about this vaccine, just like we talk about all the others. Just like we talk about getting the flu shot. There's nothing special about it now. And we are going to do it the same day that we do all the other vaccines."

Editor's note: This story updates an earlier version which incorrectly listed the approved indications for an HPV vaccine.