The vaccine against human papillomavirus (HPV) has lowered the amount of infections in teenage girls, according to researchers.

NPR reported that during the first four years of HPV immunizations, "infections from the four strains of human papillomavirus targeted by the vaccines plummeted by more than half among 14-to-19-year-olds in the United States."

According to a new study released on Wednesday, there has been a decrease of the incidence of HPV among teenage girls by 56 percent since 2006.

The vaccine caused controversy with some parents who worried about possible health risks.  Parents also were concerned that getting their daughters vaccinated would encourage earlier sexual activity.

Officials recommend girls get the HPV vaccine when they are 11 or 12, before the initiation of sexual activity because it produces the best protection. Females up to age 26 are urged to get the three-shot course if they have yet to be vaccinated.

The new study showed no decrease in the HPV strains covered by the vaccine in other age groups, which lead researchers to believe.  Researchers also found no decrease in sexual activity among females in the target population, from nearly 12 percent to a little more than five percent.

Young males up to the age of 21 are recommended to get the HPV vaccine.  The virus can cause genital warts along with penile and anal cancers in men.

According to NPR, the vaccine costs between $128 and $135 a dose, which is around $400 for the full course.  Many insurers cover HPV vaccination and some federal programs for child vaccinations give the administer the shots for free.

CDC officials reportedly intend to use the new results urge more young men and women to get HPV vaccines. The goal is for 80 percent of adolescents to get fully vaccinated.

Dr. Thomas Frieden, director of the Centers for Disease Control and Prevention, said that getting more adolescents vaccinated means cases of cervical cancers and deaths would significantly drop.

"Of girls alive today between the ages of zero and 13, there will be 50,000 more cases of cancer if we don't increase the rates to 80 percent," Frieden said. "And for every single year we delay in getting to 80 percent, another 4,400 women are going to develop cervical cancer in their lifetimes - even with good screening programs."