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

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

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.

Study Overview

• Status: Completed
• Conditions: Influenza
• Intervention / Treatment: Drug: Influenza vaccine

Detailed Description

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).

• Study Type: Interventional
• Enrollment (Actual): 134476
• Phase: Phase 4

Contacts and Locations

Study Locations

• Spain
  • A Coruña
    • Santiago de Compostela, A Coruña, Spain
      • General Public Health Directorate of Galician Health Service

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Older Adult
• Accepts Healthy Volunteers: Yes

Description

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

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: QIV-HD vaccine; EFLUELDA, Suspension for injection, one dose	Drug: Influenza vaccine; 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
Active Comparator: QIV-SD vaccine; INFLUVAC TETRA, Suspension for injection, one dose	Drug: Influenza vaccine; 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

What is the study measuring?

Primary Outcome Measures

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

Secondary Outcome Measures

Outcome Measure	Time Frame
Hospitalization for any cardio-respiratory disease [composite endpoint]	≥14 days after vaccination and up to May 31 the following year
All-cause hospitalization	≥14 days after vaccination and up to May 31 the following year
All-cause mortality	≥14 days after vaccination and up to May 31 the following year
Hospitalization for influenza	≥14 days after vaccination and up to May 31 the following year
Hospitalization for pneumonia	≥14 days after vaccination and up to May 31 the following year

Collaborators and Investigators

• Sponsor: Federico Martinón Torres

Study record dates

Study Major Dates

• Study Start (Actual): October 26, 2023
• Primary Completion (Actual): May 31, 2025
• Study Completion (Actual): May 31, 2025

Study Registration Dates

• First Submitted: October 26, 2023
• First Submitted That Met QC Criteria: November 15, 2023
• First Posted (Actual): November 21, 2023

Study Record Updates

• Last Update Posted (Actual): August 8, 2025
• Last Update Submitted That Met QC Criteria: August 4, 2025
• Last Verified: November 1, 2023

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Respiratory Tract Infections; Infections; Orthomyxoviridae Infections; RNA Virus Infections; Virus Diseases; Respiratory Tract Diseases; Influenza, Human
• Other Study ID Numbers: GALFLU

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No