Immunogenicity and safety evaluation of a newly manufactured recombinant Baculovirus-Expressed quadrivalent influenza vaccine in adults 18 years old and Above: An Open-Label, phase III extension study

In the face of global health threats, there is a growing demand for vaccines that can be manufactured on a large scale within compressed timeline. This study responds to this imperative by delving into the evaluation of FluGuard, a novel recombinant influenza vaccine developed by Nivad Pharmed Salamat Company in Iran. Positioned as a phase 3 extension, the research aimed to evaluate the safety and immunogenicity of FluGuard in volunteers aged 18 and above. The study was conducted as a single-center, open-label clinical trial. All eligible volunteers received FluGuard (2021-2022 Formula) on day 0. Safety assessments occurred at days 1, 4, 7, 14, 28 and 42 post-vaccination. Immunogenicity was measured through seroconversion, seroprotection, and geometric mean titer fold increase in subgroups of 250 volunteers. Among the 4,260 volunteers were screened and assessed for eligibility, 1000 were enrolled. At day 28 post-vaccination, seroconversion rates for A/H1N1, A/H3N2, B/Yamagata, B/Victoria were 53.4 % [95 %CI: 46.7-60], 57.7 % [95 %CI: 51.1-64.3], 54.3 % [95 %CI: 47.7-60.9], and 36.2 % [95 %CI: 29.8-42.6], respectively in volunteers 18 years and above. The most common solicited adverse events were pain at the injection site, malaise, and headache. No suspected unexpected adverse events and adverse events of special interest occurred during the study period. Our findings suggested that FluGuard® exhibits a desirable safety profile and provides sufficient immunogenicity against influenza virus types A and B. However, extended studies are warranted to assess the long-term protective efficacy. Trial Registration: The study protocol was accepted by Iranian registry of clinical trial; https://www.irct.ir; IRCT20201104049265N2.