Abstract
AbstractOlder adults (≥65 years of age) bear a significant burden of severe disease and mortality associated with influenza, despite relatively high annual vaccination coverage and substantial pre-existing immunity to influenza. To test the hypothesis that host factors, including age and sex, play a role in determining the effect of repeat vaccination and levels of pre-existing humoral immunity to influenza, we evaluated pre- and post-vaccination strain-specific hemagglutination inhibition (HAI) titers in adults over 75 years of age who received a high-dose influenza vaccine in at least four out of six influenza seasons (NCT02200276). Neither age, sex, body mass index, frailty, nor repeat vaccination were significantly associated with post-vaccination HAI titer outcomes. Pre-vaccination titers, however, were significantly predictive of post-vaccination outcomes. Pre-vaccination titers to H1N1 remained constant with age, while those to H3N2 and influenza B decreased substantially with age in males but not in females. Our findings highlight the importance of pre-existing immunity in this highly vaccinated older adult population and suggest that older males are particularly vulnerable to reduced pre-existing humoral immunity to influenza from previous annual vaccination.
Publisher
Cold Spring Harbor Laboratory
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