title: Modeling the long-term persistence of hepatitis A antibody after a two-dose vaccination schedule in Argentinean children.
abstract: BACKGROUND
  Long-term seroprotection data are essential for decision-making on the need and timing of vaccine boosters. Based on data from longitudinal serological studies, modeling can provide estimates on long-term antibody persistence and inform such decision-making.
  
  
  METHODS
  We examined long-term anti-hepatitis A virus (anti-HAV) antibody persistence in Argentinean children ≤15 years after the initial study where they completed a 2-dose course of inactivated hepatitis A vaccine (Avaxim 80U Pediatric, Sanofi Pasteur, Lyon, France). Blood serum samples were taken at baseline, 2 weeks (post first dose), 6 months (pre-booster), 6.5 months (post-booster), 10 years and 14-15 years after first vaccine dose. We fitted 8 statistical model types, predominantly mixed effects models, to anti-HAV persistence data, to identify the most appropriate and best fitting models for our data set and to predict individuals' anti-HAV levels and seroprotection rates up to 30 years post vaccination.
  
  
  RESULTS
  Fifty-four children (mean age at enrollment 30.4 months) were enrolled up to 15 years post first vaccine dose. There were 3 distinct periods of antibody concentration: rapid rise up to peak concentration post-booster, rapid decay from post-booster to 10 years, followed by slower decay. A 3-segmented linear mixed effects model was the most appropriate for the data set. Extrapolating based on the available 14-15-year follow-up, the analysis predicted that 88% of individuals anti-HAV seronegative prior to vaccination would remain seroprotected at 30 years post vaccination and lifelong seroprotection for vaccinees seropositive prior to vaccination.
  
  
  CONCLUSIONS
  Currently available data demonstrate that Avaxim 80U Pediatric confers to most vaccinees a high level of seroprotection against hepatitis A infection for at least 20-30 years.
authors.affiliation: From the *Infectious Disease Program, "Dr. Ricardo Gutiérrez" Children's Hospital, Buenos Aires, Argentina; †Sanofi Pasteur, Franchise & Product Strategy, Lyon, France; ‡Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom; §Health Economics, Evidera, London, United Kingdom; ¶Sanofi Pasteur, Global Medical Affairs, Lyon, France; and ‖Sanofi Pasteur, Global Commercial Operations, Buenos Aires, Argentina.
authors.forename: Eduardo L
authors.initials: EL
authors.lastname: López
authors.forename: María Marta
authors.initials: MM
authors.lastname: Contrini
authors.forename: Alicia
authors.initials: A
authors.lastname: Mistchenko
authors.forename: Alexia
authors.initials: A
authors.lastname: Kieffer
authors.forename: Rebecca F
authors.initials: RF
authors.lastname: Baggaley
authors.forename: Gian Luca
authors.initials: GL
authors.lastname: Di Tanna
authors.forename: Kamal
authors.initials: K
authors.lastname: Desai
authors.forename: Anvar
authors.initials: A
authors.lastname: Rasuli
authors.forename: Judith
authors.initials: J
authors.lastname: Armoni
mesh_terms: D000293:Adolescent; D000328:Adult; D001118:Argentina; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006506:Hepatitis A / Q000517:prevention & control*; D035922:Hepatitis A Antibodies / Q000097:blood*; D022362:Hepatitis A Vaccines / Q000008:administration & dosage / Q000276:immunology*; D030041:Hepatitis A virus / Q000276:immunology*; D006801:Humans; D007115:Immunization Schedule; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D015233:Models, Statistical; D013997:Time Factors; D014611:Vaccination / Q000379:methods*
chemical_list: D035922:Hepatitis A Antibodies; D022362:Hepatitis A Vaccines