Jacob BornsteinSurita RouxLone Kjeld PetersenLi Min HuangSimon R. DobsonPunnee PitisuttithumJavier Diez-DomingoAndrea SchillingHany AriffinRichard TytusRichard RuppShelly SendersEli EngelDaron FerrisYae Jean KimYoung Tae KimZafer KurugolOliver BautistaKatrina M. NolanSandhya SankaranarayananAlfred SaahAlain LuxembourgNational Taiwan University HospitalMedical College of GeorgiaEge ÜniversitesiYonsei University College of MedicineOdense UniversitetshospitalUT Medical Branch at GalvestonUniversity of Malaya Medical CentreMahidol UniversityThe University of British ColumbiaMerck & Co., Inc.Sungkyunkwan UniversityBar-Ilan UniversityClinica AlemanaBayview Research GroupSynexus Clinical Research SAFoundation for the Promotion of Health and Biomedical Research of Valencia Region (FISABIO)Senders PediatricsHamilton Medical Research Group2022-08-042022-08-042021-01-01Pediatrics. Vol.147, No.1 (2021)10984275003140052-s2.0-85099326316https://repository.li.mahidol.ac.th/handle/20.500.14594/78854BACKGROUND AND OBJECTIVES: Human papillomavirus (HPV) antibody responses to the 9-valent human papillomavirus (9vHPV) vaccine among girls and boys (aged 9-14 years) receiving 2-dose regimens (months 0, 6 or 0, 12) were noninferior to a 3-dose regimen (months 0, 2, 6) in young women (aged 16-26 years) 4 weeks after last vaccination in an international, randomized, open-label trial (NCT01984697). We assessed response durability through month 36. METHODS: Girls received 2 (months 0 and 6 [0, 6]: n = 301; months 0 and 12 [0, 12]: n = 151) or 3 doses (months 0,2, and 6 [0, 2, 6]: n = 301); boys received 2 doses ([0, 6]: n = 301; [0, 12]: n = 150); and young women received 3 doses ([0, 2, 6]: n = 314) of 9vHPV vaccine. Anti-HPV geometric mean titers (GMTs) were assessed by competitive Luminex immunoassay (cLIA) and immunoglobulin G-Luminex immunoassay (IgG-LIA) through month 36. RESULTS: Anti-HPV GMTs were highest 1 month after the last 9vHPV vaccine regimen dose, decreased sharply during the subsequent 12 months, and then decreased more slowly. GMTs 2 to 2.5 years after the last regimen dose in girls and boys given 2 doses were generally similar to or greater than GMTs in young women given 3 doses. Across HPV types, most boys and girls who received 2 doses (cLIA: 81%-100%; IgG-LIA: 91%-100%) and young women who received 3 doses (cLIA: 78%-98%; IgG-LIA: 91%-100%) remained seropositive 2 to 2.5 years after the last regimen dose. CONCLUSIONS: Antibody responses persisted through 2 to 2.5 years after the last dose of a 2-dose 9vHPV vaccine regimen in girls and boys. In girls and boys, antibody responses generated by 2 doses administered 6 to 12 months apart may be sufficient to induce high-level protective efficacy through at least 2 years after the second dose.Mahidol UniversityMedicineArticleSCOPUS10.1542/PEDS.2019-4035