Quality and quantity of the humoral immune response in healthy elderly andyoung subjects after annually repeated influenza vaccination

Doubt about the serologic efficacy of annually repeated influenza vaccinati on prompted investigations into the course of hemagglutination-inhibiting ( HI), IgG, and IgA antibody titers and the IgG and IgA avidity index to infl uenza A/Taiwan/1/86 and A/Beijing/353/89 after annual vaccination. Fifty-fo ur healthy elderly persons >70 years of age and 24 healthy young adults <30 years of age received standard influenza vaccine during 3 consecutive year s. On average, prevaccination HI, IgG, and IgA titers to both influenza vir us strains increased greater than or equal to 4 fold between the first and the third vaccination (analysis of variance, P < .001), The postvaccination HI and IgG titers remained unchanged after annual vaccination. The avidity index of IgG and IgA antibodies increased somewhat after annual vaccinatio n, although the increase was statistically significant only in the young su bjects. These data indicate that annual influenza vaccination of healthy el derly and young subjects results in an overall increase in protective antib odies.