49%

Percent of American girls who had gotten at least the first of the recommended three vaccine shots for the human papillomavirus, or HPV, a sexually transmitted virus that causes genital warts and cervical cancer. Only one-third had received all three doses by 2010, according to the CDC. Why isn't it catching on? The vaccine is expensive, for one thing, and the multiple doses make it a hassle. Also, many parents may wrongly believe that girls don't need it if they're not sexually active, or that getting the shots would require an uncomfortable talk about sex. [via AP]