CONCISE COMMUNICATIONS The Effect of Age and Natural Priming on the IgG and IgA Subclass Responses after Parenteral In¯uenza Vaccination

This study investigated the effect of natural priming and age on serum IgG and IgA subclass responses after parenteral trivalent in¯uenza vaccination. Sera from 18 young children and 8 adults were collected at various times after vaccination. An ELISA was performed to quantify the concentrations of antibody subclasses. The children were divided into primed and un-primed groups based on the presence of prevaccination serum antibodies. In both children and adults, IgG1 and IgA1 were the predominant IgG and IgA subclasses detected after vaccination. No IgG2 responses were detected in sera of unprimed children, and the pro-portion of the IgG2 response was lower in primed children than in adults. This suggests that the IgG2 immune response in young children is dependent on previous priming and may mature later than the other IgG subclasses after parenteral in¯uenza vaccination. In¯uenza is a highly contagious virus that attacks the res-piratory tract. IgG is the predominant serum immunoglobulin induced after in¯uenza immunization or infection and is cor-related with resistance to illness [1]. In humans, IgG is divided into four subclasses, IgG1, IgG2, IgG3, and IgG4, which con