The inactivated quadrivalent split-virus seasonal influenza vaccine [Fluarix® quadrivalent, manufactured in Dresden (D-QIV)] contains 15 μg haemagglutinin from each of the four influenza virus strains expected to circulate in the upcoming influenza season. Unlike seasonal trivalent influenza vaccines (TIVs), which have been used previously, quadrivalent influenza vaccines (QIVs) contain two influenza A subtype viruses and two B type viruses. As two different B viruses have co-circulated in recent years, incorporating both B lineages reduces the risk of the dominant B strain not being included in the vaccine. D-QIV is approved for active immunization of individuals aged ≥3 years to prevent disease caused by the influenza A subtype viruses and B type viruses contained in the vaccine. In large randomized, controlled trials, D-QIV was highly immunogenic in healthy adults (including individuals aged ≥65 years) and children, and exceeded the criteria for vaccine licensure. Immune responses for D-QIV, compared with those for TIVs, were non-inferior against influenza A strains and common B strains and superior against the additional B strain. D-QIV was generally well tolerated in all age groups studied and, overall, reactogenicity and tolerability were generally similar to observations with TIVs. Quadrivalent influenza vaccines are expected to offer substantial cost-effectiveness benefits in seasons where the B lineage selected for inclusion in TIVs does not match the dominant circulating strain. Thus, by incorporating both circulating influenza B lineages, vaccination with D-QIV is likely to reduce the risk of the dominant circulating B type virus not matching the strain selected for the vaccine and, therefore, more effectively protect target populations from influenza than TIVs.