TITRE III: Influenza B Immunogenicity Investigation

TITRE III: TIV Infant/Toddler Response Evaluation - Influenza B Immunogenicity Investigation

Each winter, viruses belonging to two kinds of influenza A ("A/H1N1" & "A/H3N2") and two kinds of influenza B ("B/Yamagata" & "B/Victoria") can cause illness. Historically, the yearly influenza vaccine that was recommended in children was designed to protect against both kinds of influenza A but only one kind of influenza B. In a series of trials conducted between 2008-09 and 2010-11 (TITRE I, II, and IIB), the TITRE investigators measured antibody response to influenza B in children who were primed with two doses of trivalent inactivated influenza vaccine (TIV) containing B/Yamagata. Overall, the investigators found that 2 doses of vaccine containing B/Yamagata did not adequately prime children for response to the alternate B/Victoria antigen and that subsequent vaccine doses containing B/Victoria-lineage antigen strongly boosted antibodies to the B/Yamagata antigen that was introduced during first immunization priming, but with lower responses to B/Victoria. For the first time since 2009-10, the recommended B/Victoria component of the seasonal influenza vaccine has been changed, from B/Brisbane/60/2008 to B/Colorado/60/2007 for the coming 2018-19 season. The investigators thus have a unique opportunity to clarify lineage-specific influenza B responses in a well-characterized cohort of children originally primed to Yamagata. The investigators' main interest is to assess whether TITRE I children primed with two doses of B/Yamagata in 2008-09 have since or are now capable of achieving a sufficient antibody response to B/Victoria following a single dose of 2018-19 QIV, ten years after their initial TIV B/Yamagata priming exposure.

TITRE III: Influenza B Immunogenicity Investigation

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