%0 Journal Article
%T The Effect of Age and Recent Influenza Vaccination History on the Immunogenicity and Efficacy of 2009每10 Seasonal Trivalent Inactivated Influenza Vaccination in Children
%A Sophia Ng
%A Dennis K. M. Ip
%A Vicky J. Fang
%A Kwok-Hung Chan
%A Susan S. Chiu
%A Gabriel M. Leung
%A J. S. Malik Peiris
%A Benjamin J. Cowling
%J PLOS ONE
%D 2013
%I Public Library of Science (PLoS)
%R 10.1371/journal.pone.0059077
%X Background There is some evidence that annual vaccination of trivalent inactivated influenza vaccine (TIV) may lead to reduced vaccine immunogenicity but evidence is lacking on whether vaccine efficacy is affected by prior vaccination history. The efficacy of one dose of TIV in children 6每8 y of age against influenza B is uncertain. We examined whether immunogenicity and efficacy of influenza vaccination in school-age children varied by age and past vaccination history. Methods and Findings We conducted a randomized controlled trial of 2009每10 TIV. Influenza vaccination history in the two preceding years was recorded. Immunogenicity was assessed by comparison of HI titers before and one month after receipt of TIV/placebo. Subjects were followed up for 11 months with symptom diaries, and respiratory specimens were collected during acute respiratory illnesses to permit confirmation of influenza virus infections. We found that previous vaccination was associated with reduced antibody responses to TIV against seasonal A(H1N1) and A(H3N2) particularly in children 9每17 y of age, but increased antibody responses to the same lineage of influenza B virus in children 6每8 y of age. Serological responses to the influenza A vaccine viruses were high regardless of vaccination history. One dose of TIV appeared to be efficacious against confirmed influenza B in children 6每8 y of age regardless of vaccination history. Conclusions Prior vaccination was associated with lower antibody titer rises following vaccination against seasonal influenza A vaccine viruses, but higher responses to influenza B among individuals primed with viruses from the same lineage in preceding years. In a year in which influenza B virus predominated, no impact of prior vaccination history was observed on vaccine efficacy against influenza B. The strains that circulated in the year of study did not allow us to study the effect of prior vaccination on vaccine efficacy against influenza A.
%U http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0059077