Safety and immunogenicity of an intramuscular quadrivalent influenza vaccine in children 3 to 8 y of age: A phase III randomized controlled study

Abstract

A quadrivalent, inactivated, split-virion influenza vaccine containing a strain from both B lineages (IIV4) has been developed, but its safety and immunogenicity in young children has not been described. This was a phase III, randomized, double-blind, active-controlled, multi-center study to examine the immunogenicity and safety of IIV4 in children 3-8 y of age (EudraCT no. 2011-005374-33). Participants were randomized 5:1:1 to receive the 2013/2014 Northern Hemisphere formulation of IIV4, an investigational trivalent comparator (IIV3) containing the B/Victoria lineage strain, or the licensed Northern Hemisphere IIV3 containing the B/Yamagata lineage strain. Participants who had not previously received a full influenza vaccination schedule received 2 doses of vaccine 28 d apart; all others received a single dose. 1242 children were included. For all 4 strains, IIV4 induced geometric mean haemagglutination inhibition titres non-inferior to those induced by the IIV3 comparators. For both B strains, geometric mean antibody titres induced by IIV4 were superior to those induced by the IIV3 with the alternative lineage strain. Similar proportions of participants vaccinated with IIV4 and IIV3 reported solicited injection-site reactions, solicited systemic reactions, and vaccine-related adverse events. A single vaccine-related serious adverse event, thrombocytopenia, was reported 9 d after vaccination with IIV4 and resolved without sequelae. In conclusion, in children aged 3-8 y who received one dose or 2 doses 28 d apart, IIV4 had an acceptable safety profile, was as immunogenic as IIV3 for the shared strains, and had superior immunogenicity for the additional B strain.

Keywords: children; haemagglutination inhibition; immunogenicity; phase III clinical trial; quadrivalent inactivated influenza vaccine; safety.

Figure 1.

Study design and patient flow. Participants were randomized 5:1:1 to receive IIV4, IIV3-1, or IIV3-2. IIV4 contained the 4 Northern Hemisphere 2013/2014 influenza strains recommended by the World Health Organization and the European Union: A/California/7/2009 (H1N1), A/Texas/50/2012 (H3N2), B/Brisbane/60/2008 (B Victoria lineage), and B/Massachusetts/02/20122012 (B Yamagata lineage). IIV3-1 contained both A strains and the B Victoria lineage strain. IIV3-2 contained both A strains and the B Yamagata lineage strain. All participants received one vaccination at day 0. Participants who had not received 2 doses of seasonal influenza vaccine during a previous season (i.e., unprimed participants) received a second dose of vaccine on day 28.