Updated Flu Shot Boosts Antibody Responses In Children

An updated influenza vaccine containing a novel A(H3N2) strain is associated with a modest increase in antibody responses against historical strains of influenza in children, according to a recent study.

The influenza vaccine may provide a “back-boost” to antibodies against previously encountered strains of influenza, which could potentially allow more aggressive vaccine updates in the future.
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To explore this further, the researchers assessed 124 children aged 5 to 17 years who had received the 2015-2016 inactivated influenza vaccine containing an antigenically updated A(H3N2) strain. Hemagglutination-inhibition (HI) assays were performed on pre- and post-vaccination sera.

The mean fold increase in HI titer against both the 2015-2016 vaccine strain and representative strains from two prior antigenic clusters was examined. Linear regression was used to evaluate factors associated with post-vaccination titers against historical strains. Results were adjusted for baseline titer.

Results indicated that geometric mean titers against each antigen assessed had increased significantly following vaccination, with a mean fold increase of 3.29 against the vaccine strain and 1.22 to 1.46 against historical strains. The researchers noted that response to vaccine strain was associated with increased titers after vaccination against historical strains.

“A vaccine containing an antigenically novel A(H3N2) strain modestly boosted antibody responses against historical influenza strains in children,” the researchers concluded.

—Christina Vogt

Reference:

Florek NW, Campos LM, Braun KM, et al. An updated influenza A(H3N2) vaccine generates limited antibody responses to previously encountered antigens in children [Published online December 15, 2017]. Vaccine. https://doi.org/10.1016/j.vaccine.2017.12.024.