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Completed

NCT Number: NCT06506812

Pooled Analysis of Methodologically Harmonized Pragmatic Randomized Trials of High-Dose vs. Standard-Dose Influenza Vaccine Against Severe Clinical Outcomes

This prespecified analysis will pool the datasets from two pragmatic randomized trials evaluating the relative vaccine effectiveness of high-dose vs. standard-dose influenza vaccine against severe clinical outcomes: the DANFLU-2 (A Pragmatic Randomized Trial to Evaluate the Effectiveness of High-Dose Quadrivalent Influenza Vaccine vs. Standard-Dose Quadrivalent Influenza Vaccine in Older Adults) trial and the GALFLU (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) trial. The purpose of the pooled analysis is to ensure adequate statistical power for evaluating relative vaccine effectiveness against severe clinical outcomes and to increase generalizability of the results by combining data from two countries.

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Key information

Conditions

Influenza Infections Influenza, Human Lung Diseases Orthomyxoviridae Infections Pneumonia RNA Virus Infections Respiratory Tract Diseases Respiratory Tract Infections Virus Diseases

Age range

65 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 4

Primary location

Center for Translational Cardiology and Pragmatic Randomized Trials, Department of Cardiology, Copenhagen University Hospital - Herlev and Gentofte

Hellerup, Capital Region, 2900, Denmark

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Pragmatic trials conducted to estimate the relative vaccine effectiveness of high-dose influenza vaccine compared with standard-dose influenza vaccine using the DANFLU-2 protocol or a protocol developed based on the DANFLU-2 protocol

Exclusion criteria

  • Low data quality
  • Influenza circulation threshold was not met in any of the study seasons
  • Severe under-enrollment in all seasons

Treatment and study plan

High-Dose Influenza Vaccine

Biological

For this arm, the high-dose quadrivalent influenza vaccine Efluelda®/Fluzone® High-Dose Quadrivalent will be used.

Standard-Dose Influenza Vaccine

Biological

Any standard-dose quadrivalent influenza vaccine administered in the governmental influenza vaccine programs may be used.

Primary outcomes

  1. Hospitalization for influenza or pneumonia

    Time frame: ≥14 days after vaccination up to 8 months

Secondary outcomes

  1. Hospitalization for any cardio-respiratory disease

    Time frame: ≥14 days after vaccination up to 8 months

  2. Laboratory-confirmed influenza hospitalization

    Time frame: ≥14 days after vaccination up to 8 months

  3. All-cause hospitalization

    Time frame: ≥14 days after vaccination up to 8 months

  4. All-cause mortality

    Time frame: ≥14 days after vaccination up to 8 months

  5. Hospitalization for influenza

    Time frame: ≥14 days after vaccination up to 8 months

  6. Hospitalization for pneumonia

    Time frame: ≥14 days after vaccination up to 8 months

Other outcomes

  1. Hospitalization for influenza or pneumonia (alternate definition)

    Time frame: ≥14 days after vaccination up to 8 months

  2. Hospitalization for pneumonia (alternate definition)

    Time frame: ≥14 days after vaccination up to 8 months

  3. Hospitalization for influenza (alternate definition)

    Time frame: ≥14 days after vaccination up to 8 months

  4. Hospitalization for any respiratory disease

    Time frame: ≥14 days after vaccination up to 8 months

  5. Hospitalization for any cardiovascular disease

    Time frame: ≥14 days after vaccination up to 8 months

  6. Hospitalization for myocardial infarction

    Time frame: ≥14 days after vaccination up to 8 months

  7. Hospitalization for heart failure

    Time frame: ≥14 days after vaccination up to 8 months

  8. Hospitalization for atrial fibrillation

    Time frame: ≥14 days after vaccination up to 8 months

  9. Hospitalization for stroke

    Time frame: ≥14 days after vaccination up to 8 months

  10. Major adverse cardiovascular events (MACE) defined as a composite of hospitalization for acute myocardial infarction, hospitalization for stroke, and cardiovascular death

    Time frame: ≥14 days after vaccination up to 8 months

  11. MACE defined as a composite of hospitalization for acute myocardial infarction, hospitalization for stroke, hospitalization for heart failure, and cardiovascular death (alternate definition #1)

    Time frame: ≥14 days after vaccination up to 8 months

  12. MACE defined as a composite of hospitalization for acute myocardial infarction, hospitalization for stroke, and all-cause death (alternate definition #2)

    Time frame: ≥14 days after vaccination up to 8 months

  13. Hospitalization requiring mechanical ventilation

    Time frame: ≥14 days after vaccination up to 8 months

  14. Laboratory-confirmed influenza

    Time frame: ≥14 days after vaccination up to 8 months

  15. Laboratory-confirmed pneumococcal pneumonia

    Time frame: ≥14 days after vaccination up to 8 months

  16. Laboratory-confirmed COVID-19

    Time frame: ≥14 days after vaccination up to 8 months

  17. Cardio-respiratory mortality

    Time frame: ≥14 days after vaccination up to 8 months

  18. Respiratory mortality

    Time frame: ≥14 days after vaccination up to 8 months

  19. Cardiovascular mortality

    Time frame: ≥14 days after vaccination up to 8 months

  20. In-hospital mortality

    Time frame: ≥14 days after vaccination up to 8 months

  21. Intensive care unit admission

    Time frame: ≥14 days after vaccination up to 8 months

  22. Any hospital contact associated with laboratory-confirmed influenza

    Time frame: ≥14 days after vaccination up to 8 months

  23. Any exacerbation of pre-existing chronic obstructive pulmonary disease

    Time frame: ≥14 days after vaccination up to 8 months

  24. Any exacerbation of pre-existing chronic obstructive pulmonary disease (alternate definition)

    Time frame: ≥14 days after vaccination up to 8 months

  25. Severe exacerbation of pre-existing chronic obstructive pulmonary disease

    Time frame: ≥14 days after vaccination up to 8 months

  26. Severe exacerbation of pre-existing chronic obstructive pulmonary disease (alternate definition)

    Time frame: ≥14 days after vaccination up to 8 months

  27. Any exacerbation of pre-existing asthma

    Time frame: ≥14 days after vaccination up to 8 months

  28. Any exacerbation of pre-existing asthma (alternate definition)

    Time frame: ≥14 days after vaccination up to 8 months

  29. Severe exacerbation of pre-existing asthma

    Time frame: ≥14 days after vaccination up to 8 months

  30. Severe exacerbation of pre-existing asthma (alternate definition)

    Time frame: ≥14 days after vaccination up to 8 months

  31. Exacerbation of pre-existing heart failure

    Time frame: ≥14 days after vaccination up to 8 months

  32. Exacerbation of pre-existing heart failure (alternate definition)

    Time frame: ≥14 days after vaccination up to 8 months

  33. Hospitalization for pericarditis

    Time frame: ≥14 days after vaccination up to 8 months

  34. Hospitalization for myocarditis

    Time frame: ≥14 days after vaccination up to 8 months

  35. New-onset dementia

    Time frame: ≥14 days after vaccination up to 8 months

Sponsors and collaborators

Lead sponsor

Tor Biering-Sørensen

Other

Collaborators

  • Hospital Clinico Universitario de Santiago
  • Sanofi

Registry information

Acronym: FLUNITY-HD

Important dates

Study start
2025
Primary completion
2025
Study completion
2025
First posted
Jul 18, 2024
Registry last updated
Sep 12, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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