Effectiveness of High-Dose Seasonal Influenza Vaccine in Preventing Hospitalization in Older Adults
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Reviewed by Dat Tien Nguyen, B.A, ScM.
Translated by Nhi Phuong Quynh Le, B.A |
Posted on January 19th, 2026
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Every flu season, vulnerable populations, such as the elderly, are the most heavily affected. For these older individuals, the vaccine effectiveness at preventing hospitalization, which is already low and varied, can be worse than the average population. With funding from Sanofi, a study was conducted to test the effectiveness of a higher dose influenza vaccine; the study has recently published its findings in the New England Journal of Medicine.
The clinical trial included more than 100,000 participants with an average age of 72.3 years old. A small number of these participants had at least one co-existing pulmonary morbidity such as asthma (1.1%), chronic obstructive pulmonary disorder (2.1%), and other forms of chronic lung diseases (3.6%). The study was conducted in Spain during 2 flu seasons of 2023-2024, and 2024-2025.
These elderly participants were randomly assigned to be vaccinated with the standard influenza formulation of the season or the high dose experimental version. To be specific, both formulations contain hemagglutinin antigens from all 4 seasonal flu strains of (A)H1N1, (A)H3N2, (B)Victoria, and (B)Yamagata. The only difference was in the concentration, with the standard formulation containing 15 micrograms for each strain, and the high dose version had 60 micrograms for each strain.
The researchers found that the high-dose influenza vaccine was 23.7% more effective than the standard-dose version at preventing hospitalization due to influenza-related pneumonia. Albeit that the antigen concentration is higher, there is no significant difference between the adverse effects reported between the two groups. These promising results should be replicated by future studies that can also give insight into the effectiveness of high-dose influenza vaccines across different flu seasons and in different hemispheres.
The clinical trial included more than 100,000 participants with an average age of 72.3 years old. A small number of these participants had at least one co-existing pulmonary morbidity such as asthma (1.1%), chronic obstructive pulmonary disorder (2.1%), and other forms of chronic lung diseases (3.6%). The study was conducted in Spain during 2 flu seasons of 2023-2024, and 2024-2025.
These elderly participants were randomly assigned to be vaccinated with the standard influenza formulation of the season or the high dose experimental version. To be specific, both formulations contain hemagglutinin antigens from all 4 seasonal flu strains of (A)H1N1, (A)H3N2, (B)Victoria, and (B)Yamagata. The only difference was in the concentration, with the standard formulation containing 15 micrograms for each strain, and the high dose version had 60 micrograms for each strain.
The researchers found that the high-dose influenza vaccine was 23.7% more effective than the standard-dose version at preventing hospitalization due to influenza-related pneumonia. Albeit that the antigen concentration is higher, there is no significant difference between the adverse effects reported between the two groups. These promising results should be replicated by future studies that can also give insight into the effectiveness of high-dose influenza vaccines across different flu seasons and in different hemispheres.