Immunogenicity and Safety of an Inactivated Hepatitis A Vaccine in Children With Down Syndrome

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Abstract
Objectives: Hepatitis A vaccine has not been investigated in children with Down syndrome. The aim of this study was to evaluate immunogenicity and safety of an inactivated hepatitis A vaccine in noninstitutionalized children with Down syndrome and compare their responses to those of healthy control children. Methods: An open, prospective, controlled trial of 127 children ages 1 to 12 years, 63 with Down syndrome and 64 healthy control subjects, was conducted at a single hospital. Inactivated hepatitis A virus (HAV) vaccine containing 720 enzyme-linked immunosorbent assay units of alum-adsorbed HAV was administered intramuscularly in a two-dose schedule at 0 and 6 months. Seroconversion and anti-HAV titers were measured at months 1 and 7. Results: Seroconversion rates at month 1 were 92% and 94% and geometric mean titers (GMT) were 164.02 and 160.77 mIU/mL in the Down syndrome (DS) and control groups, respectively. At month 7, seroconversion rates were 100% in both groups, with GMT of 1,719.86 and 2,344.90 mIU/mL in the DS and control groups, respectively (P = 0.117). Both doses were well tolerated and no significant adverse events observed. Local reaction at the injection site was the most common adverse event reported in both groups (15% in DS and 11% in controls). Conclusions: The authors’ data demonstrate a good response to HAV vaccination in children with DS living at home, with GMT not statistically different from that of healthy control children. HAV vaccine is well tolerated and highly immunogenic in children with DS.