HD vs SD Quadrivalent Influenza Vaccine in Adults Aged 65 to 79 Years in Galicia

Study Overview
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Brief Summary
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This pragmatic randomized trial is designed to evaluate the relative vaccine effectiveness of QIV-HD vs. QIV-SD in reducing the risk of hospitalization for influenza or pneumonia in adults 65-79 years of age in Galicia during 2023/2024 and 2024/2025 seasons.

Detailed Description
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The study is a pragmatic, registry-based, open-label, active-controlled, individually randomized trial using the infrastructure of the Regional Vaccination Program of Galicia for patient recruitment, inclusion, randomization, and vaccine administration and the Galician health registries for data collection including baseline information, follow-up data and safety monitoring. Participants will have the opportunity of receiving all the information for the trial prior to the vaccination appointment. Informed consent will be obtained during the vaccination appointment by the study team prior to their vaccine administration. The participation in the study is voluntary, and only individuals who accept signing the informed consent will be recruited. Participants may withdraw from the study at any point. The study aims to randomize at least 114.011 participants over 2 influenza seasons (2023/2024 and 2024/2025) with approximately 57,000 participants per season (pending any further potential sample size adjustments following interim analysis).

Official Title
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Pragmatic Randomized Trial to Evaluate the Effectiveness of High-Dose Quadrivalent Influenza Vaccine vs. Standard-Dose Quadrivalent Influenza Vaccine in Adults Aged 65 to 79 Years in Galicia, Spain

Conditions
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Influenza

Intervention / Treatment
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* Drug: Influenza vaccine


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 1. Age 65-79 years residing in the community (only individuals who are not eligible to receive QIV-HD as part of the standard of care) 2. Informed consent form has been signed and dated Exclusion Criteria: There are no specific exclusion criteria for this study

Ages Eligible for Study
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Minimum Age: 65 Years
Maximum Age: 79 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: QIV-HD vaccine<br>EFLUELDA, Suspension for injection, one dose | Drug: Influenza vaccine<br>* Participants will be individually randomized 1:1 to receive either QIV-HD or QIV-SD, one dose, the day of the inclusion in the trial<br>|
| Active Comparator: QIV-SD vaccine<br>INFLUVAC TETRA, Suspension for injection, one dose | Drug: Influenza vaccine<br>* Participants will be individually randomized 1:1 to receive either QIV-HD or QIV-SD, one dose, the day of the inclusion in the trial<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Occurrence of a hospitalization due to influenza or pneumonia |  | ≥14 days after vaccination and up to May 31 the following year |