New England Journal of Medicine
October 27, 2011  Vol. 365 No. 17
http://content.nejm.org/current.shtml

Original Articles
HPV Vaccine against Anal HPV Infection and Anal Intraepithelial Neoplasia
J.M. Palefsky and Others

Background
The rate of anal cancer is increasing among both women and men, particularly men who have sex with men. Caused by infection with human papillomavirus (HPV), primarily HPV type 16 or 18, anal cancer is preceded by high-grade anal intraepithelial neoplasia (grade 2 or 3). We studied the safety and efficacy of quadrivalent HPV vaccine (qHPV) against anal intraepithelial neoplasia associated with HPV-6, 11, 16, or 18 infection in men who have sex with men.