Massive study tests whether a stronger flu shot saves more seniors from hospitalization
NCT ID NCT06506812
First seen Jun 25, 2026 · Last updated Jun 26, 2026 · Updated 1 time
Summary
This study combines data from two large trials in Denmark and Spain involving over 466,000 older adults. It compares the high-dose flu vaccine (Efluelda/Fluzone High-Dose) to the standard-dose flu shot to see which better prevents severe outcomes like hospitalization for flu or pneumonia. The goal is to get clearer answers by pooling data from different countries and seasons.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- High-dose quadrivalent influenza vaccine (Efluelda/Fluzone High-Dose Quadrivalent) vs. standard-dose quadrivalent influenza vaccine
- What this could lead to
- If high-dose vaccine proves more effective, it could become the preferred flu shot for older adults, reducing hospitalizations and deaths from flu.
- What could go wrong
- This is a pooled analysis of completed trials, not a new experiment. The results may not apply to all populations or flu seasons, and high-dose vaccine may cause more local reactions.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
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Phase 4
Runs after approval, following long-term safety and how well the treatment works in everyday use.
- Participants
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466,320 people
The number who actually took part.
- Started
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May 2025
- Finished
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Aug 2025
- Lead sponsor
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Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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65 years and older
- Sex
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Anyone
- Healthy volunteers
-
Not accepted
This study is not open to healthy volunteers. The entry requirements below say who it is open to.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
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
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
-
Center for Translational Cardiology and Pragmatic Randomized Trials, Department of Cardiology, Copenhagen University Hospital - Herlev and Gentofte
Hellerup, Capital Region, 2900, Denmark
More trials for these conditions
Other studies related to the condition(s) this trial covers.
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