Just two years since the HPV vaccine was recommended for boys, acceptance may be growing faster among their parents than among parents of girls, according to local doctors and state health officials.

Rates of vaccination against the sexually transmitted disease remain lower than desirable for both genders, health officials said. The rate is much lower for boys.

In New York state, 56 percent of girls have had at least one of three recommended shots for HPV, or human papillomavirus, according to the state Health Department. Just 18 percent of boys have had one, though only one year of data is available for them.

Yet, ages-old social acceptance about teen boys’ likelihood to have sex makes the pitch to boys’ parents easier than expected. Some parents feel giving children the vaccine implies permission to have sex, pediatricians said.

”Parents of boys are much more accepting," Dr. Kenneth Kroopnick, of Prime Care Pediatrics in Guilderland, said of the HPV vaccine. "There’s still some cultural norms or feelings against females becoming sexually active."

HPV is the most common STD, according to the U.S. Centers for Disease Control and Prevention. Approximately 79 million Americans are infected. Many people don’t have symptoms, making it possible for them to pass on HPV without knowing it.

The virus is perhaps best known for causing genital warts. It is the leading cause of cervical cancer and causes some cancers of the vagina, vulva, penis, anus, tonsils and tongue.

Because cervical cancer is more common than the other types, the vaccine arguably provides greater protection against disease for girls. HPV vaccine has been recommended for girls since 2006.

When CDC officials recommended it for boys in 2011, one rationale was to reduce the spread of the virus to girls, who were not getting vaccinated at high rates. But officials also said the vaccine would likely prevent other types of cancer associated with HPV.

The vaccine is most effective at preventing disease for both genders — approaching 100 percent — when all three recommended doses are received before having any sexual contact, doctors and health officials said. Health officials recommend the vaccine be given at age 11 or 12, with the doses generally given over six months.

Local parents responding to a post on the Times Union’s Facebook page had a range of opinions about getting their children vaccinated against HPV, regardless of their children’s gender.

Some said they vaccinated their adolescent kids without pause ("better safe than sorry," said one). Others expressed resistance to all vaccines or to one that hasn’t been in use for long.

Still others were worried the vaccine would make their children ill, or even kill them. At least one website claims teenage girls have died from getting the vaccine.

Doctors and health officials said these fears are unwarranted. Actual side effects include soreness around the shot site and sometimes fever, according to the CDC. Teens who died after getting the vaccine likely had some other underlying cause, said Debra Blog, director of the state Health Department’s Division of Epidemiology.

”That’s the tragedy in my mind," Blog said, "that people are more concerned about false safety concerns than they are about preventing cervical cancer in their children or themselves."

Some parents delay the shot, finding 11 or 12 too young for worries about a sexually transmitted disease, pediatricians said.

Kroopnick finds the recommended age reasonable. Even the most involved parents cannot forecast when a child will engage in sex, he said.

”If you could predict when your child is going to be sexually active and count back six months from that, then we’d have it all figured out," Kroopnick said.

Studies show that as many as half of 14-year-olds engage in some sexual activity, said Dr. Janice Pride-Boone, a pediatrician at Seton Health in Troy and Clifton Park. Many teens and their parents don’t understand that HPV can be transmitted not only through intercourse, but also skin-to-skin genital contact and oral sex, she said.

”There are apps for hooking up now," she said. "The rate of sexual activity is increasing, not decreasing."

Girls are as much at risk as boys, despite many parents’ attitudes, Pride-Boone added.

”They’re having sex with each other," she quipped.

How long the vaccine remains effective is also a question among parents considering when to give it. Current studies, which have followed girls for four to six years, show protection does not wane, Blog said.

© 2013 The New York Times Company