NCT05517174

A Pragmatic Randomized Trial to Evaluate the Effectiveness of High-Dose Quadrivalent Influenza Vaccine vs. Standard-Dose Quadrivalent Influenza Vaccine in Older Adults

• Status: Completed
• Phase: Phase 4
• Study type: Interventional
• Enrollment: 332,438 (actual)
• Sponsor: Tor Biering-Sørensen · Academic / Other
• Sex: All
• Age: 65 Years
• Healthy volunteers: Accepted

Summary

The purpose of this pragmatic randomized trial is to evaluate the relative vaccine effectiveness of high-dose quadrivalent influenza vaccine (QIV-HD) vs. standard-dose quadrivalent influenza vaccine (QIV-SD) in older adults. Participants will be randomized 1:1 to either QIV-HD or QIV-SD.

Detailed description

The study is a pragmatic, registry-based, open-label, active-controlled, individually randomized trial. The Danish nationwide administrative health registries will be used for data collection including baseline information, follow-up data, and safety monitoring. The study aims to randomize 339,700 participants over 3 influenza seasons. In each season, participants will be individually randomized 1:1 to receive either QIV-HD or QIV-SD. During the 2023/2024 and 2024/2025 seasons, up to 12,000 participants will be enrolled in a sub-cohort where participants are asked to perform home self-swabs and answer symptom questionnaires in case of influenza-like illness to enable further assessment of the impact of QIV-HD vs. QIV-SD on patient-reported outcomes among individuals with influenza-like illness and laboratory-confirmed influenza.

Conditions

• Influenza

Interventions

Type	Name	Description
BIOLOGICAL	High-Dose Quadrivalent Influenza Vaccine	For this arm, the high-dose quadrivalent influenza vaccine Efluelda®/Fluzone® High-Dose Quadrivalent will be used.
BIOLOGICAL	Standard-Dose Quadrivalent Influenza Vaccine	Any standard-dose quadrivalent influenza vaccine administered in the Danish governmental influenza vaccine program may be used.

Timeline

• Start date: 2022-09-22
• Primary completion: 2025-05-31
• Completion: 2025-08-31
• First posted: 2022-08-26
• Last updated: 2025-09-12

Locations

2 sites across 1 country: Denmark