Safety and immunogenicity of a quadrivalent intradermal influenza vaccine in adults

An intradermal (ID) trivalent split-virion influenza vaccine (IIV3-ID) (Fluzone® Intradermal, Sanofi Pasteur, Swiftwater, PA) has been available in the US since the 2011/2012 influenza season for adults aged 18–64 years. This study examined whether adding a second B-lineage strain affects immunogenicity and safety. This randomized, double-blind, multicentre trial evaluated the immunogenicity and safety of an intradermal quadrivalent split-virion influenza vaccine (IIV4-ID) in adults 18–64 years of age in the US during the 2012–2013 influenza season. Participants were randomized 2:1:1 to receive a single injection of IIV4-ID, licensed IIV3-ID, or an investigational IIV3-ID containing the alternate B-lineage strain. Haemagglutination inhibition antibody titres were assessed in two-thirds of participants before vaccination and 28 days after vaccination. 1672 participants were vaccinated with IIV4-ID, 837 with licensed IIV3-ID, and 846 with an investigational IIV3-ID. For all four vaccine strains, antibody responses to IIV4-ID were statistically non-inferior to the response to the IIV3-ID vaccines containing the matched strains. For both B strains, post-vaccination antibody responses to IIV4-ID were statistically superior to the responses to IIV3-ID lacking the corresponding B strain. Adverse events were similar for IIV4-ID and IIV3-ID. The most commonly reported solicited reactions were pain, pruritus, myalgia, headache, and malaise; and most were grade 1 or 2 and appeared and resolved within 3 days of vaccination. IIV4-ID was statistically non-inferior to the two pooled IIV3-ID vaccines for the proportions of participants with at least one grade 2 or 3 systemic reaction. Antibody responses to the IIV4-ID were non-inferior to IIV3-ID for the A and matched B strains and superior for the unmatched B strains. IIV4-ID was well tolerated without any safety concerns. IIV4-ID may help address an unmet need due to mismatched B strains in previous influenza vaccines.