Massive flu vaccine trial: does a stronger shot protect seniors better?
NCT ID NCT05517174
First seen Jun 25, 2026 · Last updated Jun 26, 2026 · Updated 1 time
Summary
This large study tested whether a high-dose flu vaccine works better than the standard-dose shot in adults 65 and older. Over 332,000 participants were randomly assigned to receive either the high-dose or standard-dose vaccine. Researchers tracked hospitalizations for flu, pneumonia, and other serious illnesses to see which vaccine offered stronger protection.
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 (QIV-HD)
What this could lead to
If high-dose vaccine works better, it could become the standard flu shot for older adults, reducing hospitalizations and deaths from flu.
What could go wrong
The trial is large and completed, but results may show only a small benefit or none. High-dose vaccine can cause more local side effects like soreness.
Disclaimer
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This is a summary of
the original study
.
Summaries may miss details or leave out important information. Before applying or accepting participation, make sure you have read and understood the full study. Curemydisease.com takes no responsibility whatsoever for anything missed, misunderstood, or acted upon as a result of our summary — we know it does not capture everything.
This is a summary of the original study . Summaries may miss details or leave out important information. Before applying or accepting participation, make sure you have read and understood the full study. Curemydisease.com takes no responsibility whatsoever for anything missed, misunderstood, or acted upon as a result of our summary — we know it does not capture everything.
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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
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Locations
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Center for Translational Cardiology and Pragmatic Randomized Trials, Department of Cardiology, Copenhagen University Hospital - Herlev and Gentofte
Hellerup, Capital Region, 2900, Denmark
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Danske Lægers Vaccinations Service
Søborg, 2860, Denmark