Background: The quadrivalent (types 6, 11, 16, and 18) human papillomavirus (HPV) L1 virus-like-particle vaccine was 95%-100% effective in preventing cervical and genital disease related to HPV-6, -11, -16, and -18. Vaccine efficacy is thought to be mediated by humoral immunity. Here, we analyze the effect of the baseline characteristics of subjects on vaccine-induced immune responses.
Methods: Immunogenicity data from 12,343 subjects 9-26 years old randomized to quadrivalent HPV vaccine or placebo in phase 2/3 studies were analyzed. Covariates examined were day 1 HPV serostatus, age, race/ethnicity, region of residence, lactation status, hormonal contraceptive usage, smoking status, Pap test diagnosis, immunosuppressant or anti-inflammatory agent use, and number of sex partners. Anti-HPV responses were summarized as serum anti-HPV-6, -11, -16, or -18 geometric mean titers 1 month after dose 3.
Results: Age at vaccination initiation was inversely proportional to the vaccine-induced anti-HPV response. Vaccination of subpopulations of subjects who were seropositive at day 1 to a vaccine HPV type resulted in more robust anti-HPV responses to that type, compared with those in subjects who were seronegative at baseline. Anti-HPV responses were comparable among the remaining demographic subgroups.
Conclusions: The immunogenicity of quadrivalent HPV vaccine was comparable among subjects with differing baseline characteristics. These data support vaccination with quadrivalent HPV vaccine across a broad range of baseline subject characteristics.