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Hum Vaccin Immunother
. 2025 Dec;21(1):2578084.
doi: 10.1080/21645515.2025.2578084. Epub 2025 Oct 29. Reactogenicity, safety, and immunogenicity of a quadrivalent seasonal influenza vaccine in adults aged 65 years and older: Phase 4 study results from India during December 2023-February 2024
Vishal Jain 1 , Frédéric Cauwberghs 2 , Hanzhu Qian 1 , Kerri Best-Sule 1 , Vinay Gupta 3 , Elie Ngantcha Tatchou 2 , Frank Struyf 2
Affiliations
Fluarix Tetra is a quadrivalent seasonal influenza vaccine that has been approved in India for immunization of adults and children aged ≥6 months. This study was conducted in adults aged ≥65 years in India to fulfill a post-approval regulatory commitment. In this prospective, multicenter, single-arm, open-label, Phase 4 study, participants were administered a single 0.5-mL dose of Fluarix Tetra (2023-2024 Northern Hemisphere). The primary objectives were to assess the reactogenicity and safety of Fluarix Tetra by monitoring solicited adverse events (AEs) within 7 days post-vaccination, as well as unsolicited AEs and serious AEs (SAEs) within 21 days post-vaccination. The secondary objective was to evaluate immunogenicity by monitoring the geometric mean titers, geometric mean increase, seroconversion rates (SCRs), and seroprotection rates (SPRs). Overall, 250 adults aged ≥65 years (mean age, 71.8 years) were included in the study. Pain (15.0%) was the most common solicited injection-site AE, and fever (6.5%) was the most common solicited systemic AE. No SAEs were reported within the 21-day post-vaccination period, and no deaths occurred during the study. The hemagglutination inhibition titers increased from Day 1 to Day 22 against all the four influenza strains, A/(H1N1), A/(H3N2), B/Yamagata, and B/Victoria, with SPRs > 80% and SCRs > 75% at Day 22. Fluarix Tetra was well tolerated and immunogenic in adults aged ≥65 years in India.Trial registration: NCT05648357.
Keywords: Quadrivalent seasonal influenza vaccine; geometric mean titer; immunogenicity; mean geometric increase; seroconversion rate; seroprotection rate.
. 2025 Dec;21(1):2578084.
doi: 10.1080/21645515.2025.2578084. Epub 2025 Oct 29. Reactogenicity, safety, and immunogenicity of a quadrivalent seasonal influenza vaccine in adults aged 65 years and older: Phase 4 study results from India during December 2023-February 2024
Vishal Jain 1 , Frédéric Cauwberghs 2 , Hanzhu Qian 1 , Kerri Best-Sule 1 , Vinay Gupta 3 , Elie Ngantcha Tatchou 2 , Frank Struyf 2
Affiliations
- PMID: 41159757
- PMCID: PMC12574568
- DOI: 10.1080/21645515.2025.2578084
Fluarix Tetra is a quadrivalent seasonal influenza vaccine that has been approved in India for immunization of adults and children aged ≥6 months. This study was conducted in adults aged ≥65 years in India to fulfill a post-approval regulatory commitment. In this prospective, multicenter, single-arm, open-label, Phase 4 study, participants were administered a single 0.5-mL dose of Fluarix Tetra (2023-2024 Northern Hemisphere). The primary objectives were to assess the reactogenicity and safety of Fluarix Tetra by monitoring solicited adverse events (AEs) within 7 days post-vaccination, as well as unsolicited AEs and serious AEs (SAEs) within 21 days post-vaccination. The secondary objective was to evaluate immunogenicity by monitoring the geometric mean titers, geometric mean increase, seroconversion rates (SCRs), and seroprotection rates (SPRs). Overall, 250 adults aged ≥65 years (mean age, 71.8 years) were included in the study. Pain (15.0%) was the most common solicited injection-site AE, and fever (6.5%) was the most common solicited systemic AE. No SAEs were reported within the 21-day post-vaccination period, and no deaths occurred during the study. The hemagglutination inhibition titers increased from Day 1 to Day 22 against all the four influenza strains, A/(H1N1), A/(H3N2), B/Yamagata, and B/Victoria, with SPRs > 80% and SCRs > 75% at Day 22. Fluarix Tetra was well tolerated and immunogenic in adults aged ≥65 years in India.Trial registration: NCT05648357.
Keywords: Quadrivalent seasonal influenza vaccine; geometric mean titer; immunogenicity; mean geometric increase; seroconversion rate; seroprotection rate.