Incidence of Genital Warts Among Men in the Placebo Arm of a Quadrivalent HPV Vaccine Efficacy Trial

Background: Quadrivalent HPV (types 6/11/16/18) vaccine (qHPV vaccine; GARDASIL®) is 90% (95% CI: 69, 98) efficacious against vaccine HPV type related external genital lesions in men. 

Objectives: The purpose of this analysis was to examine the incidence of and HPV types identified in external genital warts (EGW) among heterosexual men (HM) and men having sex with men (MSM) enrolled in an efficacy trial of qHPV vaccine.

Methods: Of 4,065 men aged 16-26 years with <5 lifetime sexual partners enrolled in a randomized, double-blind clinical trial, 2,030 received placebo.  Subjects underwent genital exams and HPV sampling from the penis, scrotum, and perineal/perianal area at day 1, month 7 and every 6 months afterwards. An incident case of EGW was defined as a subject who had no reported history or a diagnosis of EGW at day 1, but developed a subsequent EGW. 

Results: Inclusive of 2.9 years of follow-up (median), 83 cases of EGW were identified with an incidence rate (per 100 person years) of 1.83. The incidence rate among HM (1.50) was lower than in MSM (4.70).  The incidence rate was 1.12 per 100 person years (0.97-HM, 2.79-MSM) in subjects PCR and seronegative to all 4 vaccine HPV types at enrollment.  HPV types 6 and 11 were the most common HPV types found in EGW lesions with 48 (58%) and 24 (29%) cases, respectively.  

Conclusions: These data demonstrate the high incidence of EGW amongst a population of young men with few prior sexual partners.

Implications for Programs, Policy, and/or Research: These data suggest a potential benefit of male vaccination with qHPV vaccine through prevention of EGW.