Safety and immunogenicity of a quadrivalent inactivated influenza vaccine compared to licensed trivalent inactivated influenza vaccines in adults

► Two distinct lineages of influenza B virus co-circulate annually. ► The B lineage chosen for TIV is often not the B lineage that circulates. ► QIV contains two influenza B strains, one from each lineage. ► QIV was as safe and immunogenic as licensed TIV in adults. ► QIV should offer protection against both B lineages simultaneously.