There are distinct differences in the U.S. Food and Drug
Administration's (FDA) licensing for the 2 HPV vaccines
currently available. The quadrivalent vaccine (HPV4 [Gardasil,
Merck & Co., North Wales, Pennsylvania]) protects against types
6, 11, 16, and 18, and is FDA-approved for both females and
males aged 9 to 26 years (9). The bivalent vaccine (HPV2
[Cevarix, GlaxoSmithKline, Research Triangle Park, North
Carolina]) protects against types 16 and 18 but is FDA-approved
only for females (10). Both vaccines prevent cervical cancer;
however, only HPV4 is FDA-approved for prevention of vulvar,
vaginal, and anal cancer. Efficacy of the HPV4 vaccine for anal
intraepithelial neoplasia in MSM ranges from 50% to 78% (11).
Only HPV4 protects against genital warts. Although the rationale
for protection is certainly plausible, clinical HPV vaccine data
are not available for oropharyngeal cancer, recurrent
respiratory papillomatosis, or penile cancer (9 - 10).