CompletedPhase 4

Dynamics of the Immune Responses to Repeat Influenza Vaccination Exposures

Hong Kong977 participantsStarted 2020-10-05

Plain-language summary

The aims of this vaccine trial are: (1) to measure humoral and selected cellular immune responses to repeated influenza vaccination with Flublok, including these responses' associations with age, birth year, and prior vaccination history; (2) to identify the characteristics of study participants who are vaccinated but still become infected with influenza virus ("vaccine failures") and participants who have poor immune responses to vaccination; and (3) to predict how influenza vaccinations and infections shape immunity.

Who can participate

Age range

18 Years – 45 Years

Sex

ALL

See this in plain English?

AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.

Inclusion Criteria: * Aged 18-45 years at enrolment. * Capable of providing informed consent. * Resident in Hong Kong in the coming 2 years. Exclusion Criteria: * Vaccinated against influenza in the past 24 months. * Included in one of the priority groups to receive influenza vaccination in Hong Kong (priority groups include pregnant women, long-stay residents of institutions for persons with disability, persons with chronic medical problems (chronic cardiovascular, lung, metabolic or kidney diseases, obesity (body mass index 30 or above) and chronic neurological condition), healthcare workers or persons working in poultry, pig farming or pig slaughtering industry). * With diagnosed medical conditions related to their immune system. * Currently taking medication for any condition that impairs immune system. * 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; 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 no…

Questions worth asking your doctor

Bring these to your next appointment. They're a starting point for a shared conversation — not a sign you qualify or a recommendation to enrol.

1Based on my diagnosis and history, is this trial worth exploring for me — or is there a standard treatment we should try first?
2What does this trial's phase tell us about how much is already known about its safety and benefit?
3What would taking part actually involve for me — visits, tests, time, and travel?
4What are the known and possible risks or side effects I should weigh, and how would they be monitored?
5If this trial isn't the right fit, what other options or trials would you suggest I look into?

Generated to help you prepare — always confirm anything about your own eligibility and care with the study team and your doctor.

Questions for the trial coordinator

The trial coordinator is the person who runs the study day to day. These cover the practical side — logistics, costs, and what taking part would actually mean for your life. The study team confirms whether you meet the criteria; these are questions to ask, not a sign you qualify.

1What does taking part actually involve week to week — how many visits, where, and how long does each one take?
2What costs are covered by the study, and what might I have to pay for myself, including travel, parking, or time off work?
3What happens during screening, and what happens if the study team confirms I don't meet the criteria after those tests?
4Who pays for the scans, blood work, and other tests the trial requires — the study, my insurance, or me?
5How will being in the trial affect my regular care, and will my own doctor stay informed and involved?
6Can I leave the trial at any point if I change my mind, and what would happen to my care if I do?

A starting point for the conversation — always confirm anything about your own eligibility, costs, and care with the study team and your doctor.

What they're measuring

Immune response to vaccination (4-fold rise in titer at day 30)

Timeframe: 30 days after vaccination

Immune response to vaccination (GMT ratio at day 30 and 182)

Timeframe: 30 days and 182 days after vaccination

Trial details

NCT IDNCT04576377

SponsorThe University of Hong Kong

Sponsor typeOTHER

Study typeINTERVENTIONAL

Primary completion2025-12-31

View on ClinicalTrials.gov More Influenza, Human trials