The newly approved vaccine works by preventing infection by four of the dozens of strains of the human papillomavirus, or HPV, the most prevalent sexually transmitted disease. The Food and Drug Administration licensed it for use in girls and women 9 to 26. It is still being studied in males.
Gardasil protects against the two types of HPV responsible for about 70 percent of cervical cancer cases. The vaccine also blocks infection by two other strains responsible for 90 percent of genital wart cases, the AP reports.