Immunogenicity and safety levels of inactivated quadrivalent influenza vaccine in healthy adults via meta-analysis.

: The aim of the current study was to evaluate immunogenicity and safety levels of human inactivated quadrivalent influenza vaccine (QIV) which includes two A strains (A/H1N1, A/H3N2) and two B lineages (B/Victoria, B/Yamagata) in healthy adults via meta-analysis. : Searches were conducted in PubMed, Cochrane Library, ClinicalTrials.gov, and EMBASE databases published in 2011-2020 according to inclusion and exclusion criteria. The purpose was to collect and perform meta-analysis of related randomized clinical trial (RCT) data concerning safety and immunogenicity levels of human QIV compared with inactivated trivalent influenza vaccine (TIV). : A total of 9 literatures were included. There was no significant difference in the seroconversion(SCR) and seroprotection(SPR) between QIV and TIV for influenza A strains (A/H1N1, A/H3N2) and the B lineage included in the TIV. QIV showed superior efficacy for the B lineage not included in the TIV: SCR RR of 2.20 (95%CI: 1.44-3.37, = .0003) and SPR RR of 1.34 (95%CI: 1.10-1.63, = .004) for B/Victoria, and SCR RR of 1.88 (95%CI: 1.53-2.31, < .00001) and SPR RR of 1.11 (95%CI: 1.03-1.19, = .006) for B/Yamagata, respectively. There were no significant differences between QIV and TIV for local and systemic adverse events(AE) post-vaccination. : In adults 18-64 years old, QIV not only produced similar immunogenicity and safety levels to TIV, but also had better immunogenicity against influenza B vaccine strains not included in TIV.