The impact of pre‐existing influenza antibodies and inflammatory status on the influenza vaccine responses in older adults.

Age‐associated immune changes and pre‐existing influenza immunity are hypothesized to reduce influenza vaccine effectiveness in older adults, although the contribution of each factor is unknown. Here, we constructed influenza‐specific IgG landscapes and determined baseline concentrations of cytokines typically associated with chronic inflammation in older adults (TNF‐α, IL‐10, IL‐6, and IFN‐γ) in 30 high and 29 low influenza vaccine responders (HR and LR, respectively). In a background of high H3 antibody titers, vaccine‐specific H3, but not H1, antibody titers were boosted in LRs to titers comparable to HRs. Pre‐vaccination concentrations of IL‐10 were higher in LRs compared with HRs and inversely correlated with titers of pre‐existing influenza antibodies. Baseline TNF‐α concentrations were positively correlated with fold‐increases in antibody titers in HRs. Our findings indicate that baseline inflammatory status is an important determinant for generating post‐vaccination hemagglutinin‐inhibition antibodies in older adults, and IgG responses can be boosted in the context of high pre‐existing immunity. [ABSTRACT FROM AUTHOR]