What is the HPV vaccine?
The HPV vaccine, called Gardasil, protects girls and women against HPV (human papillomavirus), the most common sexually transmitted infection in the U.S. Experts estimate that more than 50 percent of sexually active people will get HPV at some point in their lives. HPV is easily passed from person to person through genital contact (and can even be transmitted while using condoms).
There are more than 100 strains of HPV, though most cause no symptoms and go away on their own as the immune system fights them off. But some HPV strains may linger and cause genital warts or changes to cells in the cervix that can lead to cervical cancer over time. The majority of cases of cervical cancer are caused by HPV infection.
The HPV vaccine protects against four strains of HPV: Two that cause genital warts, and two that cause about 70 percent of all cervical cancer cases.