• Jin Hyang Kim, Margarita Mishina, Jessie R Chung, Kelly Stefano Cole, Mary Patricia Nowalk, Judith M Martin, Sarah Spencer, Brendan Flannery, Richard K Zimmerman, and Suryaprakash Sambhara.
• Influenza Division, Centers for Disease Control and Prevention.
• J. Infect. Dis. 2016 Oct 1; 214 (7): 1030-8.

BackgroundEmergence of antigenically drifted influenza A(H3N2) viruses resulted in reduced vaccine effectiveness in all age groups during the 2014-2015 influenza season. In children, inactivated influenza vaccine (IIV) elicited neutralizing antibodies (Abs) against drifted strains at significantly lower levels than against the vaccine strain. Little is known about the cross-reactivity of cell-mediated immunity against drifted strains in children.MethodsChildren aged 3-17 years (n = 48) received IIV during the 2014-2015 influenza season. Peripheral blood mononuclear cells, collected before (on day 0) and after (on days 7 and 21) vaccination were evaluated for induction of cross-reactive plasmablasts, memory B cells, and cytokine-secreting CD4(+) and CD8(+) T cells against the vaccine and drifted A(H3N2) viruses by an enzyme-linked immunospot assay and flow cytometry.ResultsIIV increased frequencies of plasmablasts and memory B cells. The overall induction of the T-cell response was not significant. Both B-cell and T-cell responses showed significant cross-reactivity against A(H3N2) viruses. Age and preexisting immunity affected virus-specific plasmablast responses and fold-change of T-cell responses, respectively. The proportion of T-helper type 1-prone (ie, interferon γ- or tumor necrosis factor α-secreting) CD4(+) T cell responses also increased with age.ConclusionsIn children aged 3-17 years, B- and T-cell responses following IIV receipt showed significant cross-reactivity against A(H3N2) viruses during a vaccine mismatch season.Published by Oxford University Press for the Infectious Diseases Society of America 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.

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