 The study compared the lot-to-lot consistency, immunogenicity, and safety of a 2014-2015 northern hemisphere quadrivalent split virion inactivated influenza vaccine, IIV4, with that of a trivalent inactivated influenza vaccine, IIV3, in younger and older adults. The study found that the three IIV4 lots had equivalent post-vaccination hemagglutination inhibition antibody titers, and that the pooled IIV4s were non-inferior to IIV3 for all vaccine strains except for the B-strain lineage when absent from the comparator IIV3. The study also found that IIV4 increased seroneutralizing antibody titers against all three vaccine strains of influenza and had a similar safety profile as the licensed IIV3, with solicited injection site reactions being mostly grade 1 and transient. This article was authored by Saini Sese, Jersey Brasostek, Indomaya, and others.