Federal officials announced on Thursday that one in four girls in the United States had their shot against cervical cancer. This is the government’s first study of vaccination rates for the Gardasil vaccine. This vaccine protects young girls and women against the sexually transmitted human papilloma virus, or the HPV. The strains of this virus cause 70% of cervical cancer.

The doctors advise girls’ parents to have their daughters vaccinated when they are 11 or 12 years old, before they start their sexual life. They also say 11 years old is the age when kids have to do a lot of vaccines.

This study tracked only children with ages between 13 and 17. The ones who proposed this vaccine in girls so little aged have said that this could reduce the number of cervical cancer cases with 4,000 women. Still, as Patti Gravitt, a Johns Hopkins University associate professor of epidemiology, said, many parents are somehow concerned about the safety of the vaccine.

The shots are very expensive, about $375, but many health insurers have started to cover for them. Other questions are the ones connected to the fact that vaccines don’t offer lifetime immunity and if this happens, a booster may be needed. Gravitt said that "some parents may be adopting the attitude with their daughters that, 'Well, you're still young. I can wait a couple more years before you're sexually active.'"