IntroductionThe approved schedules for human papilloma virus (HPV) vaccines (qHPV (Gardasil®) and bHPV (Cervarix®)) include three doses administered at 0, 1-2 and 6 m. The first two doses given within a relatively short period of time are expected to prime the immune system and the third is expected to confer long-lasting immunity.1 When given according to this schedule to 16-45 y old females, HPV vaccines have been shown to be highly immunogenic and protect against persistent infection, anogenital warts and precancerous abnormalities.2-10 Post-licensure trials with bHPV showed that > 98% of 15-25 y old females developed antibodies to HPV 16 and HPV 18 which remain detectable up to 76 mo after a single vaccine dose.3 In addition, a significant increase in antibody titers resulted from a second dose of vaccine and high clinical efficacy was demonstrated in individuals who received less than three vaccine doses. [4][5][6] Finally, in preadolescents and adolescents, both HPV and combined HAV/HBV vaccines Background. No immunogenicity data has been reported after a single dose of the quadrivalent HPV vaccine (qHPVGardasil®) and no data are available on co-administration of this vaccine with the HAV/HBV vaccine (Twinrix-Junior®). Two pre-licensure studies reported similar anti-HPV but lower anti-HBs titers when co-administering HPV and HBV vaccines.Objectives. To assess the immunogenicity of the qHPV and HAV/HBV vaccine when co-administered (Group-co-adm) or given one month apart (Group-sep) and to measure the persistence of HPV antibodies three years post-second dose of qHPV vaccine in both study groups.Methods. 416 9-10 year-old girls were enrolled. Vaccination schedule was 0-6 months. Anti-HAV and anti-HBs were measured in all subjects 6 months post-first dose and 1 month post-second dose. Anti-HPV were measured 6 months post-first dose in Group-co-adm and in all subjects 1 and 36 months post-second dose.Results. six months post-first dose: 100% of subjects had detectable anti-HAV and 56% and 73% had detectable antiHBs in Group-co-Adm and Group-sep, respectively. In Group-co-adm 94, 100, 99 and 96% had detectable antibodies to HPV 6, 11, 16 and 18, respectively. One month post-second dose of qHPV and HAV/HBV vaccine, in both study groups 99.5-100% of subjects had an anti-HAV titer ≥ 20IU/L, 97.5-97.6% an anti-HBs level ≥ 10IU/L, and 100% had an anti-HPV titer ≥ 3LU. Thirty-six months post-second dose of qHPV all but four subjects (99%) had antibodies to HPV18 and 100% had antibodies to HPV6, 11 and 16. The great majority (97-100%) had an anti-HPV titer ≥ 3 LU. Post-second dose administration of qHPV and HAV/HBV, no meaningful difference was observed in the immune response in the two study groups to any component of vaccines.conclusions. The results indicate that qHPV and HAV/HBV can be given during the same vaccination session. Two doses of of qHPV and HAV/HBV vaccines induce a strong immune response. Three years post-second dose of qHPV, the great majority of subjects had antibodies to HPV types included in the v...