The vaccine is designed to block four of the most common strains of the sexually transmitted human papilloma virus, or HPV.
Gardasil is already approved for preventing cervical cancer and genital warts in females aged 9 to 26, and for preventing genital warts in males aged 9 to 26.
One of the new studies shows Gardasil is about 89 percent effective in blocking cervical cancer, genital warts and lingering HPV infections in women aged 24 to 45. The other shows it is about 77 percent effective in blocking anal cancer and precancerous lesions in homosexual men.
Merck will seek approval to sell the vaccine for those uses. It funded both studies.
Merck & Co. tested its Gardasil vaccine so it can seek approval to market the vaccine for two new uses, blocking cervical cancer in women over age 26 and preventing anal cancer in homosexual men.
Three Gardasil doses in women up to age 45 reduced by 89 percent the risk of getting precancerous lesions on the cervix, genital warts or a persistent HPV infection.
Gardasil prevented anal cancer and precancerous lesions of the anus in 77 percent of young men.