After four years on the market,  the HPV vaccine has a low acceptance rate, health officials say. 

The disease: Human papillomavirus is a sexually transmitted virus that causes a variety of cancers in men and women, but primarily cervical cancer.

Prevalence: There are more than 6 million new cases each year. Half of both men and women are infected at some point by age 50. The disease clears in most people, but some get cancer.

The vaccine: It's recommended for girls starting at age 11, before they become sexually active, because women are at much greater risk for cancer. But it also protects boys.

Cost: Each of three shots, administered over six months, costs about $120. Most health plans cover it for women. Those without insurance can get financial assistance at public health clinics and Planned Parenthood. Josephine Marcotty