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Antibody to hepatitis A antigen was detected, by radiommuncassay, in sera froom 455 hospitalized children and adolescents without a liver disease or a clinically recognizable hepatitis history. The positive rate of antibody was over 90% in newborn infants and then progressively decreased and reached its lowest level, 9.1%, at age 7-12 months. The high positive rate in newborn infants is... |