Why your annual flu shot might work differently each year
NCT ID NCT04576377
First seen Jun 25, 2026 · Last updated Jun 27, 2026 · Updated 1 time
Summary
This completed study in Hong Kong enrolled 977 adults aged 18-45 to understand how getting the flu vaccine year after year changes the body's immune response. Participants received either the Flublok vaccine or a saline placebo. Researchers measured antibody levels and looked for reasons why some vaccinated people still catch the flu. The goal is to improve future flu vaccination strategies.
What this could mean
Our plain-language read of the trial. This is informational only — not medical advice or a prediction.
Active substance
Flublok (recombinant quadrivalent influenza vaccine)
What this could lead to
If successful, this study could help predict who benefits most from annual flu shots and why some vaccinated people still get the flu.
What could go wrong
This is an observational knowledge-harvesting study, not a test of a new treatment. Results may not apply to older adults or other populations.
Disclaimer
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This is a summary of
the original study
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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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The University of Hong Kong
Hong Kong, 00000, Hong Kong