How repeat influenza vaccinations affect immune responses
The Dynamics of the Immune Responses to Repeat Influenza Vaccination Exposures (DRIVE III) Study - a Randomized Controlled Trial
This trial will test whether repeat use of Flublok (injection) and FluMist (nasal spray) changes the strength and breadth of immune responses in adults aged 22–50 in Hong Kong.
Quick facts
| Phase | Phase 4 |
|---|---|
| Study type | Interventional |
| Enrollment | 600 (estimated) |
| Ages | 22 Years to 50 Years |
| Sex | All |
| Sponsor | The University of Hong Kong Academic / other |
| Locations | 1 site (Hong Kong) |
| Trial ID | NCT07240922 on ClinicalTrials.gov |
What this trial studies
This randomized Phase 4 trial will enroll 600 adults in Hong Kong and assign them to one of four groups receiving combinations of live attenuated nasal vaccine (FluMist) or placebo and injected recombinant hemagglutinin vaccine (Flublok) or placebo. The design includes participants who previously took part in DRIVE I/II and participants who have not received influenza vaccination in the prior two years. Researchers will measure antibody and cellular immune responses to compare magnitude, breadth, and durability across groups and to identify biological mechanisms underlying variable vaccine responses. The setting in a population with low vaccine coverage aims to reduce confounding from long-standing repeat vaccination histories.
Who should consider this trial
Good fit: Healthy adults aged 22–50 who live in Hong Kong and either participated in DRIVE I/II or have not received an influenza vaccine in the past two years are ideal candidates.
Not a fit: People in Hong Kong priority vaccination groups (for example, pregnant people, those with chronic medical conditions, healthcare workers), immunocompromised individuals, and those outside the 22–50 age range are not eligible and unlikely to benefit from participation.
Why it matters
Potential benefit: If successful, this work could help guide vaccination strategies that produce broader and stronger protection against influenza for adults.
How similar studies have performed: Prior trials and observational studies have reported repeat-vaccination effects and differences in immunogenicity, but randomized trials combining FluMist and Flublok in a low-coverage Hong Kong population are limited.
Eligibility criteria
Show full inclusion / exclusion criteria
Inclusion Criteria: 1. Aged 22-50 years at enrolment. 2. A. Participated in the DRIVE I or DRIVE II studies (for DRIVE IIIa). OR B. Did not participate in the DRIVE I or DRIVE II study (for DRIVE IIIb) and has not received influenza vaccination in the prior two years. 3. Capable of providing informed consent. 4. Resident in Hong Kong in the coming 2 years. Exclusion Criteria: 1. 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). 2. With diagnosed medical conditions related to their immune system. 3. Currently taking medication for any condition that impairs immune system. 4. 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. 5. Individuals who report medical conditions not suitable to receive live attenuated vaccines, such as: * having asthma; * having close contact with severely immunosuppressed persons who require a protected environment; or * having immunosuppressive treatment (e.g. high-dose steroid, anti-cancer drugs and radiotherapy). 6. 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). 7. Individuals who have any medical conditions not suitable to receive inactivated or live attenuated influenza vaccines as determined by a clinician.
Where this trial is running
Hong Kong
- School of Public Health, The University of Hong Kong — Hong Kong, Hong Kong (Recruiting)
Study contacts
- Principal investigator: Benjamin J Cowling, PhD — The University of Hong Kong
- Study coordinator: Benjamin J Cowling, PhD
- Email: bcowling@hku.hk
- Phone: +852 39176711
How to participate
- Review the eligibility criteria above with your treating physician.
- Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
- Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.