The vaccine for human papillomavirus, or HPV, provides pre-teens and teenagers with a safe and effective prevention of some cancers that can be traumatic, according to three Gainesville medical professionals at a forum on the subject Thursday. “This vaccine is not a sex vaccine; it is a cancer vaccine,” said Dr. Andrew Green, a gynecological oncologist who specializes in cancer of the cervix, uterus and ovary, at a the monthly WomenSource Power Lunch on Brenau University’s downtown campus.