VIENNA – Vaccination with Gardasil effectively prevented external genital and anal lesions in a multicenter, placebo-controlled study of more than 4,000 men aged 16-26 years followed for 2 years.
Recipients also showed good tolerance for the standard three-dose course of vaccine over 6 months, with an adverse event profile similar to that of placebo, Dr. Heiko Jessen said at the 18th International AIDS Conference.
The quadrivalent Gardasil vaccine, which immunizes against human papillomavirus (HPV) strains 6, 11, 16, and 18, already has approval from the Food and Drug Administration for use in boys and men aged 9-26 years for preventing condyloma acuminata, as well as in girls and women aged 9-26 years. But the U.S. Advisory Committee on Immunization Practices recommends routine immunization against human papillomavirus only for girls and women.
The new study was funded by Merck, which markets Gardasil. The study ran at 95 sites in 18 countries, including several sites in the United States.
The study enrolled 3,463 heterosexual men aged 16-23 years and 602 men who have sex with men (MSM) aged 16-26 years. All enrollees were seronegative to the four vaccine strains at baseline, and their blood remained negative in polymerase chain reaction tests through month 7 of the study, at the end of the vaccination series. The participants all also had no visible genital lesions at enrollment, and no history of genital warts. All participants who qualified for the per protocol analysis received three doses of the vaccine: at baseline and after 2 and 6 months.
The safety analysis included 1,945 men who received the HPV vaccine and 1,950 men in the placebo group. The incidence of all vaccine-related adverse experiences was 64% in the vaccine group and 58% in the placebo group. Systemic vaccine-related adverse experiences occurred in 14% of the vaccine recipients and 15% of the control group. Serious adverse experiences occurred in less than 1% of the participants in each treatment group, and no one had a serious, vaccine-related adverse experience.
Assessment of vaccine efficacy for preventing external genital lesions involved the entire study enrollment. Three of the 1,399 men who received the vaccine per protocol had external lesions during the 2 years following vaccination, all condylomas. Thirty-one of the 1,408 men in the placebo group had lesions, including 28 with condylomas, 2 with grade 1 penile/perianal/perineal intraepithelial neoplasia, and 1 person with a higher-grade lesion. The results showed a vaccine efficacy rate of 90%, reported Dr. Jessen, a physician based in Berlin and a coinvestigator on the study.
Analysis of the incidence of anal intraepithelial neoplasia (AIN) and anal cancer focused on the MSM population in the study. Among 194 MSM who met the per protocol specifications, 5 developed AIN related to one of the vaccine HPV types, compared with 24 of 208 MSM in the placebo group, producing a vaccine efficacy of 78%. None of the study participants developed anal cancer.
Additional analysis looked at the incidence of persistent HPV infection by strains 6, 11, 16, or 18 during follow-up, which occurred in 15 vaccine recipients and 101 controls, a vaccine efficacy for this end point of 86%.
Dr. Jessen did not report any disclosures. Two of his coauthors on the study are employees of Merck.