Gardasil is a widely available vaccine against certain types of the human papillomavirus (HPV), a virus that infects skin and mucous membranes in humans. Gardasil was developed by Merck, and is effective against four types of HPV: types 6 and 11, which are responsible for 90 percent of cases of genital warts in females, and types 16 and 18, which are responsible for approximately 70 percent of cervical cancer cases.

The vaccine consists of virus-like particles very similar to HPV, that, when injected, cause an immune response that generates antibodies against HPV. When administered appropriately (three doses within a six-month period) Gardasil is nearly 100 percent effective in preventing the development of precancerous cervical cells. Gardasil is effective for at least four years, and some preliminary ...