title: Hepatitis A vaccination of Argentinean infants: comparison of two vaccination schedules.
abstract: BACKGROUND
  Early immunization to protect infants against hepatitis A (HA) is recommended in intermediate or high endemic areas of the world, but little is known of the effects of maternal antibodies on the immune response. We studied the immunogenicity and reactogenicity of an inactivated HA vaccine administered in two different schedules to 2-month-old infants in an intermediate/high endemic area in Argentina.
  
  
  METHODS
  In this double-blind, randomized study 131 infants received either three doses (at 2, 4, 6 months of age [Group A]) or one dose (at 6 months of age [Group B]) of the pediatric inactivated HA vaccine, Avaxim 80, and a booster dose at 15-18 months. HAV antibodies were measured (ELISA) at 2, 7, 15-18 and 16-19 months of age. Immediate (30 min after injection) and solicited local and systemic reactions were recorded for 7 days after each injection.
  
  
  RESULTS
  Of 107/131 subjects (81.6%) who completed the study and who provided final serum samples after booster dose, 94 (87.8%) were seropositive at enrolment (>20 mIU/mL) with geometric mean concentrations (GMC) of 2989 and 3637 mIU/mL in Groups A and B, respectively. One month post-booster GMCs were 8236 mIU/ml (95% CI; 6304, 10760) and 1687 mIU/ml (1148, 2479) in Groups A and B, respectively, with 100% seroprotection.
  
  
  CONCLUSIONS
  The HA vaccine was well tolerated and induced immunological priming in both groups during the first year of life in spite of the presence of maternal antibodies. Post-booster GMCs achieved after one or three primary doses suggest a long-term protection against HA.
authors.affiliation: Hospital de Niños Ricardo Gutiérrez, Guido 2676, Piso 10, 1425 Buenos Aires, Argentina. eduardoluislopez@fibertel.com.ar
authors.forename: E L
authors.initials: EL
authors.lastname: López
authors.forename: M M
authors.initials: MM
authors.lastname: Contrini
authors.forename: M C
authors.initials: MC
authors.lastname: Xifró
authors.forename: M A
authors.initials: MA
authors.lastname: Cattaneo
authors.forename: B
authors.initials: B
authors.lastname: Zambrano
authors.forename: R
authors.initials: R
authors.lastname: Dumas
authors.forename: N
authors.initials: N
authors.lastname: Rouyrre
authors.forename: F
authors.initials: F
authors.lastname: Weber
mesh_terms: D001118:Argentina; D004311:Double-Blind Method; D005260:Female; D006506:Hepatitis A / Q000276:immunology / Q000517:prevention & control*; D035922:Hepatitis A Antibodies / Q000097:blood*; D022362:Hepatitis A Vaccines / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology; D006801:Humans; D007112:Immunity, Maternally-Acquired; D007115:Immunization Schedule; D007117:Immunization, Secondary; D007223:Infant; D008297:Male; D014611:Vaccination
chemical_list: D035922:Hepatitis A Antibodies; D022362:Hepatitis A Vaccines