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Which flu shot works best for seniors? hong kong study seeks answers

NCT ID NCT03330132

Prevention Sponsor: The University of Hong Kong Source: ClinicalTrials.gov ↗

What the study statuses mean

This study's is highlighted.

Recruitment status, easiest to join first

Recruiting now
This trial is taking on new participants right now.
Not yet recruiting
Registered, but not yet taking participants.
By invitation only
Not open to general applications. Only people the study team invites can take part.
Paused
Paused for now. It may or may not start again.
Ongoing
Running, but no longer taking on new participants.
Completed This study
The trial has finished. Results may not be published yet.
Stopped early
Stopped early, before it reached the end. That can be for many reasons, including safety.
Cancelled
Cancelled before anyone took part.

Expanded access (not trials)

Expanded access
Not a trial. This treatment can be requested outside a study, case by case, for people who qualify.
Expanded access (paused)
Not a trial. The treatment can normally be requested outside a study, but is unavailable right now.
Expanded access (ended)
Not a trial. The treatment could once be requested outside a study, but no longer can.
Approved
The treatment has been approved, so it is available normally rather than through this programme.

When the status isn't known

Details not published
The full record has not been published yet, so there is little to show here.
Status unknown
This status has not been confirmed recently, so it may be out of date.

First seen Jun 27, 2026 · Last updated Jun 27, 2026

Summary

This study tested several types of flu vaccines in over 1,800 adults aged 65-82 in Hong Kong over four years. The goal was to see which vaccine or combination of vaccines provides the strongest and longest-lasting immune protection. Researchers measured antibody levels and immune cell responses to find the best annual vaccination strategy for older adults.

What this could mean

Our plain-language read of the trial. This is informational only, not medical advice or a prediction.

Active substance
Influenza vaccines (standard, adjuvanted, high-dose, and recombinant)
What this could lead to
If successful, this could identify a more effective annual flu vaccination strategy for older adults, reducing flu cases and complications.
What could go wrong
This is a completed Phase 4 trial, so results are available but may not apply to other regions or age groups. Different flu strains each year could also affect how well the findings hold up.

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

Phase 4

Runs after approval, following long-term safety and how well the treatment works in everyday use.

Participants

1,861 people

The number who actually took part.

Started

Oct 2017

Finished

Dec 2025

Lead sponsor

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

65 to 82 years

Sex

Anyone

Healthy volunteers

Accepted

You do not need to have the condition being studied to take part.

Show 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: • Adult aged 65-82 years attending ECC and EDC who has not received 2017/18 seasonal influenza vaccine and is willing to receive annual influenza vaccination Exclusion Criteria: * Individuals who show signs of dementia (do not pass the Mini-cog test under Appendix 1a: Recruitment Screening Log) or significant cognitive impairment and are not competent to give their consent. * Individuals who report medical conditions not suitable to receive inactivated influenza vaccines, such as: * Severe allergic reaction (e.g., anaphylaxis) after previous dose of any influenza vaccine; or to a vaccine component, including egg protein; * Moderate or severe acute illness with or without fever after any previous influenza vaccination; or * A history of Guillain-Barré syndrome (GBS) within 6 weeks of previous influenza vaccination. * Individuals, who report medical conditions not suitable to receive intramuscular injection, such as: * bleeding disorders * habitually taking anticoagulants (with the exception of antiplatelets such as aspirin). * Individuals who have any medical conditions not suitable to receive inactivated influenza vaccines as determined by a clinician.

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Conditions

The condition(s) this trial relates to.

influenza prevention target

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

Influenza, human

Contacts and locations

Locations

  • The University of Hong Kong

    Hong Kong, China

More trials for these conditions

Other studies related to the condition(s) this trial covers.