Long-term antibody persistence in children after vaccination with the pediatric formulation of an aluminum-free virosomal hepatitis A vaccine.
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 1-7 years old than in subjects 8-17 years old and higher in females 11-17 years old than in males 11-17 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.
From the *Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium; †Department of Public Health, Ghent University, Ghent, Belgium; ‡GZA Campus Sint-Vincentius, Antwerp, Belgium; §Crucell Holland BV, Leiden, The Netherlands; and ¶Crucell Switzerland AG, Bern, Switzerland.
Koen
K
Van Herck
Annick
A
Hens
Ilse
I
De Coster
André
A
Vertruyen
Jeroen
J
Tolboom
Michal
M
Sarnecki
Pierre
P
Van Damme
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D035922:Hepatitis A Antibodies / Q000097:blood*; D022362:Hepatitis A Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D006801:Humans; D007118:Immunoassay; D007223:Infant; D008137:Longitudinal Studies; D013997:Time Factors; D014611:Vaccination / Q000379:methods*; D022721:Vaccines, Virosome / Q000008:administration & dosage* / Q000276:immunology*
D035922:Hepatitis A Antibodies; D022362:Hepatitis A Vaccines; D022721:Vaccines, Virosome; C530970:epaxal berna