Gardasil is a vaccine that is administered to prevent certain strains of human papillomavirus (HPV). Several strains of HPV exist, many of which are harmless and only cause infections that clear up on their own. Some strains, however, can cause longer lasting infections that can later manifest as cancer. Most people do not develop any signs or symptoms of the infection, meaning it is often unknowingly transmitted between sexual partners.

Some HPV strains have been shown to cause cervical cancer, vulvar cancer, vaginal and anal cancer. In the majority of cases, HPV infects girls and women aged between 9 and 45 years.

The infective strains that are particularly harmful include types 6, 11, 16 and 18, with strains 16 and 18 thought to cause up to 70% of cervical cancers and types 6 and 11 thought to cause up to 90% of genital warts cases.

Genital warts are irregular, skin colored growths around the genitals. They may be found inside or outside of the genitals in both men and women. The warts can be painful, itch and may even start to bleed.

Cancer of the cervix usually begins with changes in the cellular appearance of the cervical inner lining. These changes can usually be detected using a Pap Test. These are precancerous lesions that, with time, may turn into cancer and spread to other organs (undergo metastasis) or even cause death.

Even when a person is infected with HPV, Gardasil vaccination is still advised, to protect against different HPV strains in the future.

Gardasil is available as injections that can be given to females between the ages of 9 and 45 years and males aged between 9 and 26 years. It is estimated that the majority of individuals who have sexual intercourse will be infected with HPV at some point. Therefore, all sexually active males and females are at risk of HPV infection.

As well as protecting against HPV strains 6, 11, 16 and 18, Gardasil also offers some degree of protection against HPV types 31, 33, 52, 56, 58, and 59.