Influenza hemagglutination-inhibiting antibodies in hospitalized children. Distribution of specific activity into IgM, IgG and IgA classes.

Sera from 75 children hospitalized with a clinical diagnosis of acute respiratory virus disease were tested by hemagglutination-inhibition as regards influenza A2 and B antibody shifts. In 48 patients there was an antibody shift during the clinical evolution of the disease (against influenza A2 in 34, B-- in 11, A2 and B in 3cases). A significant proportion of sera with antibody shift associated with a decrease of serum IgG levels and with an increase of serum IgM and IgA levels.