Long-term antibody persistence in children after vaccination with the pediatric formulation of an aluminum-free virosomal hepatitis A vaccine
Faculty of Medicine and Health Sciences
The pediatric infectious disease journal. - Baltimore, Md
, p. E85-E91
University of Antwerp
Background: The pediatric dose of the virosomal hepatitis A vaccine Epaxal®, Epaxal® Junior, is safe and immunogenic in children from 1 to 17 years of age. The present study investigated the long-term immunogenicity of Epaxal® Junior. The standard doses of Epaxal® and aluminum-adsorbed hepatitis A vaccine (Havrix® Junior) were used as comparators. Methods: A total of 271 children who had completed a 0/6-month immunization schedule (priming and booster dose) participated in this follow-up study. Anti-hepatitis A virus (HAV) antibody levels were measured using a microparticle enzyme immunoassay (HAVAB 2.0 Quantitative; Abbott Diagnostics, Wiesbaden, Germany) starting at 18 months following the second dose, and then yearly until 66 months (ie, 5.5 years) after the second dose. Results: All subjects tested at Month 66 still had protective anti-HAV antibodies (>=10 mIU/mL). Antibody titers were generally lower in subjects 17 years old than in subjects 817 years old and higher in females 1117 years old than in males 1117 years old. In addition, an age-dependent decay was observed, that is, antibody decreased more rapidly in younger than in older children. Conclusions: Vaccination of children with two doses of Epaxal® Junior confers a real-time protection of at least 5.5 years. This protection is estimated to last approximately 25 years. Younger children showed lower antibody titers and a faster antibody decline than older children. Additional follow-up studies are needed beyond 5.5 years to further assess the long-term immunogenicity of Epaxal® Junior.