Immunogenicity and safety of quadrivalent recombinant influenza vaccine in Korean adults: Phase III, randomized study

Quadrivalent recombinant influenza vaccine (RIV4) is indicated for active immunization against influenza virus in adults (≥18 years) in countries where it is currently registered. This Phase III, parallel, randomized, modified double-blind, active controlled, multi-center study was designed to compare the immunogenicity and safety of single dose intramuscular RIV4 with a locally-licensed quadrivalent-inactivated influenza vaccine (IIV4, Fluarix® quadrivalent) in participants aged ≥18 years during 2021-22 Northern Hemisphere influenza season at three tertiary care centers in South Korea. Participants were randomized (1:1) to receive single dose intramuscular RIV4 or IIV4. All participants were centrally assigned to randomized study intervention using an interactive response technology (IRT). Participants, investigators, and the staff in-charge of the sampling, safety assessment and immunogenicity assays were blinded. The overall mean age of 300 participants who completed the study was 46.1 years. The post-vaccination geometric mean fold-rise of HAI antibodies were 32.0, 13.2, 6.1, and 5.3 in RIV4 group, and 22.3, 8.0, 4.7, and 3.4 in IIV4 group for the A/H1N1, A/H3N2, B/Victoria lineage, and B/Yamagata lineage strains, respectively. Seroconversion in RIV4 was comparable or higher than IIV4. Neither immediate unsolicited AEs were reported within 30 min of vaccination nor SAEs, AESIs nor deaths were reported during the 6-month follow-up. Clinical Trial Registration:ClinicalTrials.gov number - NCT05144945.