ATLANTA (AP) — Disappointed health officials say only about half of teenage girls have gotten a controversial vaccine against cervical cancer — a rate that's changed little in three years.

The Centers for Disease Control and Prevention reported Thursday that about 54 percent of teenage girls have received at least one dose of the expensive three-shot vaccine. The shots protect against human papilloma virus, or HPV. The sexually transmitted bug can cause cervical cancer and genital warts.

The vaccine was introduced in 2006, and is recommended at ages 11 and 12. Some experts think parents are uneasy with the sexual issues it raises, and doctors and states have hesitated to promote it or require it for school attendance.

The new report is based on a telephone survey.

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