High-Dose Influenza Vaccine to Reduce Hospitalizations

Area of Science:

• Gerontology
• Vaccinology
• Epidemiology

Background:

• High-dose inactivated influenza vaccine (HD-IIV) demonstrated superior protection against laboratory-confirmed influenza in adults 65+ compared to standard-dose vaccine.
• Limited data exist on HD-IIV's effectiveness against severe clinical outcomes like hospitalization in this age group.

Purpose of the Study:

• To evaluate the relative effectiveness of HD-IIV versus standard-dose influenza vaccine against severe clinical outcomes in community-dwelling adults aged 65 to 79.
• To assess the impact of HD-IIV on hospitalization rates for influenza or pneumonia.

Main Methods:

• A pragmatic, open-label, randomized, active-controlled trial was conducted over two influenza seasons (2023-2024, 2024-2025) in Galicia, Spain.
• 103,169 participants were randomized 1:1 to receive either HD-IIV or standard-dose vaccine.
• The primary endpoint was a composite of hospitalization for influenza or pneumonia.

Main Results:

• A primary endpoint event occurred in 0.26% of participants receiving HD-IIV versus 0.34% receiving standard-dose vaccine (relative vaccine effectiveness, 23.7%).
• Hospitalization for influenza specifically occurred in 0.09% of the HD-IIV group versus 0.14% of the standard-dose group (relative vaccine effectiveness, 31.8%).
• Serious adverse events were similar between the two groups.

Conclusions:

• HD-IIV was associated with fewer hospitalizations for influenza or pneumonia compared to the standard-dose vaccine in adults aged 65 to 79.
• The findings suggest HD-IIV offers enhanced protection against severe influenza-related outcomes in this demographic.