Immunogenic Properties and Safety of a Quadrivalent Inactivated Subunit Adjuvanted Influenza Vaccine in Adults Aged 18 to 85 Years at the End of the COVID-19 Pandemic in the 2022–2023 Season
Kostinov M.P. Kostinova A.M. Iushkova S. Gladkova L. Vlasenko A. Dagil Y. Kvasova M. Kameleva A. Kachnova A. Solovеva I. Khamidulina A. Prutskova E. Mekhantseva I. Andreeva N. Polishchuk V.B. Mana Y.A. Kostinov A.M.
February 2026Multidisciplinary Digital Publishing Institute (MDPI)
Vaccines
2026#14Issue 2
Background: SARS-CoV-2 infection has raised concerns about altered immune responses, creating a need to evaluate influenza vaccine performance in the post-COVID period. This study aimed to compare the immunogenicity and safety of a quadrivalent inactivated subunit adjuvanted influenza vaccine in adults aged 18–85 years during the 2022–2023 season. Methods: A total of 144 adults were enrolled: group 1, aged 18–59 years (n = 124), and group 2, aged 60–85 years (n = 20). All received a quadrivalent inactivated subunit adjuvanted vaccine containing 5 μg of each influenza antigen and 500 μg of Azoximer bromide. IgG antibodies to vaccine strains were measured at baseline and days 30–32 using the hemagglutination inhibition assay. Participants were actively monitored for adverse events by telephone. Results: The Geometric Mean Fold Increase (GMFI) met the efficacy criteria in both age groups (≥2.5 for 18–59 years and ≥2.0 for 60–85 years), with no significant differences. The seroprotection rate reached accepted thresholds for most strains but was below criteria for B/Victoria in the 18–59 group (48%) and for B/Phuket in the 60–85 group (35%). Significant between-group differences were observed for B/Victoria (p = 0.01) and B/Phuket (p = 0.007). Seroconversion met criteria for all strains in younger adults, but for older adults, it was insufficient for B/Phuket (20%, below the ≥30% threshold; p = 0.05 vs. 18–59 years). Local reactions occurred in 24.2% and systemic in 11.3% of younger adults; in older adults, in 20% and 15%, respectively. All resolved spontaneously within 1–3 days. Conclusions: The quadrivalent adjuvanted influenza vaccine demonstrated acceptable immunogenicity and safety in adults aged 18–85 years despite potential post-COVID immune alterations.
adjuvanted influenza vaccine , adults , azoximer bromide , immunogenicity , influenza , SARS-CoV-2 infection , vaccination
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Department of Epidemiology and Modern Vaccination Technologies, I. M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, 119991, Russian Federation
I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, 105064, Russian Federation
Moscow Health Department, D. D. Pletnev City Clinical Hospital, Moscow, 105077, Russian Federation
Federal State Budgetary Educational Institution of Higher Education, Samara State Medical University, The Ministry of Healthcare of the Russian Federation, Samara, 443079, Russian Federation
National Research Center, Institute of Immunology of the Federal Medical Biological Agency of Russia, Moscow, 115522, Russian Federation
Federal State Budgetary Educational Institution of Higher Education, Privolzhsky Research Medical University, Ministry of Health of the Russian Federation, Nizhniy Novgorod, 603005, Russian Federation
Department of Clinical Immunology, Allergology and Adaptology, P. Lumumba Russian University of Peoples’ Friendship, Moscow, 117198, Russian Federation
Department of Pediatrics, Institute of Medicine, Ecology and Physical Culture, Ulyanovsk State University, Federal State Budgetary Educational Institution of Higher Education, Ulyanovsk, 432007, Russian Federation
Department of Internal Medicine, Karaganda Medical University, Karaganda, 100012, Kazakhstan
Department of Healthcare Management and Economics, The Chuvash State University Named After I. N. Ulyanov, Federal State Educational Establishment of Higher Professional Education, Cheboksary, 428015, Russian Federation
Budgetary Institution “City Children’s Clinical Hospital”, Ministry of Health of the Chuvash Republic, Cheboksary, 428000, Russian Federation
Department of Epidemiology and Modern Vaccination Technologies
I. I. Mechnikov Research Institute of Vaccines and Sera
Moscow Health Department
Federal State Budgetary Educational Institution of Higher Education
National Research Center
Federal State Budgetary Educational Institution of Higher Education
Department of Clinical Immunology
Department of Pediatrics
Department of Internal Medicine
Department of Healthcare Management and Economics
Budgetary Institution “City Children’s Clinical Hospital”
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