The science behind the HPV vaccine

If you watched the CNN/Tea Party debate last night, you saw Rep. Michelle Bachmann and Rick Santorum ganging up on front-runner Gov. Rick Perry.

They were slamming the Texas governor for his 2007 order that required 12-year-old girls in his state to get vaccinated against HPV – a virus that can cause cervical cancer.

This morning on American Morning, CNN's Elizabeth Cohen explains what the vaccine is and why it's causing so much controversy.