Text Box: IMMUNOGENICTY PEDIATRIC FORUMULATION OF VAQTAÔ IN KOREA Sohn YM, Lee JS, Park JH, Park MS, LeeWS*, Poerschke G*, Kuter B*, Evans K*; Yonsei University, Seoul, Korea; MSD Korea*, MSD Asia Ltd.*, Merck Research Lab., PA, USA* Objective: To assess the immunogenicity, safety and tolerability of VAQTAÔ [Hepatitis A [HA] vaccine, purified inactivated, MSD] in healthy children and adolescents. Methods: Eligible subjects ages 2 to 17 years received 25U/0.5 mL of VAQTAÔ, IM, at 0 and 24 weeks. Serum samples were obtained prior to dose 1 to ascertain serostatus and 4 weeks after the 2nd dose to ascertain immunogenicity of the 2-dose series. To detect antibody response to HAV after vaccination with VAQTAÔ, a modification of the Abbot HAVABÒ kit was used. Samples with titers ³ 10 mIU/mL were considered seropositive. Adverse Events were monitored for 14 days after each injection. Results: 102 subjects [54 male, 48 female] were enrolled. The mean age was 6.8 ¡À 3.5 years. Two subjects were seropositive, 2 were lost to follow-up and after 2nd dose 10 withdrew. 88 subjects were available for a per protocol analysis and 90 for all subjects with serology. All subjects seroconverted 4 weeks after dose 2. Geometric mean titer was 7991.1 mIU/mL [95% CI 6481.1 to 9852.7) with very little difference in per protocol and all subjects analysis. Adverse reactions to VAQTA were generally mild and transient. Conclusions: This was the first evaluation of the CR326F strain derived hepatitis A vaccine in Korea. The pediatric two-dose regimen of VAQTAÔ was found to be highly immunogenic, generally well tolerated and resulted in 100% seroconversion. Routine vaccination should be considered to effectively control the increasing disease burden of HAV seen in Korea 2410