Clinical trials of Gardasil 9, the only HPV vaccine available in the U.S., has shown that it provides nearly 100% protection against cervical infections with HPV strains 16 and 18. Gardasil 9 has also been found to be almost 100% effective in preventing cervical, vulvar, and vaginal disease caused by HPV strains 31, 33, 45, 52, and 58.
Not all HPV strains cause cancer, but the four with the highest risk of cervical cancer include strains 6, 11, 16, and 18. There are other strains of HPV that can also cause cancer, but they are considered lower risk and include 31, 33, 45, 52, and 58. Strains 16 and 18 cause almost three-fourths of all cancers, whereas strains 6 and 11 cause the majority of genital warts.
Gardasil 9 has also been shown to prevent anal cell changes in men caused by infection and genital warts. Current guidelines recommend all children between ages 11-12 should get two injections of the vaccine roughly six to 12 months apart. The Gardasil 9 vaccine is recommended for men up to age 21 and young women up to age 26.