Cross-lineage influenza B antibody responses measured by HI and MN assays.*

HI = hemagglutination inhibition; MN = microneutralization; TIV = trivalent inactivated influenza vaccine. Note that undetectable titres *Unit of analysis pooled sera from 5 mice, thus 10 pools from 50 mice were available for this experiment.aMeasured two weeks after specified TIV dose;bMeasured two months after specified TIV dose.†Compared to pre-immunization for initiating antigens; compared to immediately preceding titre for boosting antigens.Yamagata = Florida/4/06(Yamagata)-like, the Yamagata lineage antigen included in the northern hemisphere 2008–09 TIV.Victoria = Brisbane/60/08(Victoria)-like, the Victoria lineage antigen included in the northern hemisphere 2009–10 and 2010–11 TIV.