title: Kinetics of maternally acquired anti-hepatitis A antibodies: prediction of waning based on maternal or cord blood antibody levels.
abstract: BACKGROUND
  Timing is critical for efficient hepatitis A vaccination in high endemic areas as high levels of maternal IgG antibodies against the hepatitis A virus (HAV) present in the first year of life may impede the vaccine response.
  
  
  OBJECTIVE
  To describe the kinetics of the decline of anti-HAV maternal antibodies, and to estimate the time of complete loss of maternal antibodies in infants in León, Nicaragua, a region in which almost all mothers are anti-HAV seropositive.
  
  
  METHODS
  We collected cord blood samples from 99 healthy newborns together with 49 corresponding maternal blood samples, as well as further blood samples at 2 and 7 months of age. Anti-HAV IgG antibody levels were measured by enzyme immunoassay (EIA). We predicted the time when antibodies would fall below 10 mIU/ml, the presumed lowest level of seroprotection.
  
  
  RESULTS
  Seroprevalence was 100% at birth (GMC 8392 mIU/ml); maternal and cord blood antibody concentrations were similar. The maternal antibody levels of the infants decreased exponentially with age and the half-life of the maternal antibody was estimated to be 40 days. The relationship between the antibody concentration at birth and time until full waning was described as: critical age (months)=3.355+1.969 × log(10)(Ab-level at birth). The survival model estimated that loss of passive immunity will have occurred in 95% of infants by the age of 13.2 months.
  
  
  CONCLUSIONS
  Complete waning of maternal anti-HAV antibodies may take until early in the second year of life. The here-derived formula relating maternal or cord blood antibody concentrations to the age at which passive immunity is lost may be used to determine the optimal age of childhood HAV vaccination.
authors: Institute of Social and Preventive Medicine, University of Bern, Finkenhubelweg 11, CH-3012 Bern, Switzerland.
authors: Martin W G
authors: MW
authors: Brinkhof
authors: Orlando
authors: O
authors: Mayorga
authors: Jürgen
authors: J
authors: Bock
authors: Ulrich
authors: U
authors: Heininger
authors: Christian
authors: C
authors: Herzog
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005312:Fetal Blood / Q000276:immunology*; D035922:Hepatitis A Antibodies / Q000097:blood*; D030041:Hepatitis A virus / Q000276:immunology*; D006801:Humans; D007112:Immunity, Maternally-Acquired; D007124:Immunoenzyme Techniques; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D009527:Nicaragua; D011247:Pregnancy; D013997:Time Factors; D055815:Young Adult
chemical_list: D035922:Hepatitis A Antibodies; D007074:Immunoglobulin G