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1000
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Abstract/Summary
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Background!#!There are limited data regarding the duration of immunity induced by different human papillomavirus (HPV) vaccination schedules and the immunogenicity of a booster dose of both bivalent HPV vaccine (bHPV) or quadrivalent HPV vaccine (qHPV).!##!Methods!#!Follow-up of a nonrandomized clinical trial to evaluate the 5-year antibody persistence of the bHPV in girls (age, 9-10 years) and women (age, 18-24 years). Noninferiority of the 2-dose versus 3-dose schedule among girls was evaluated at months 54 (n = 639) and 64 (n = 990). Girls vaccinated with a 2-dose schedule of bHPV or qHPV received a booster dose of either vaccine at month 61. Immunogenicity was measured using a virus-like particle-based enzyme-linked immunosorbent assay. Geometric mean titers (GMTs) for HPV16/18 were estimated after stratification by vaccination schedule and age group.!##!Results!#!At months 54 and 64, the 2-dose schedule remained noninferior to the 3-dose schedule. GMTs remained above natural infection levels across all age groups up to 64 months. After the booster, anti-HPV16/18 GMTs increased exponentially with the same pattern, regardless of vaccine administered. No safety concerns were identified with the booster dose.!##!Conclusions!#!A 2-dose schedule is highly immunogenic in girls, suggesting a high immune memory. Thus, a booster dose is likely to be unprofitable, considering the low global immunization coverage.!##!Clinical trials registration!#!NCT01717118.
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