Influenza APhase 4NCT06567860
Characterizing Late-season Influenza Vaccine Responses to Compare the 2023 and 2024 Vaccine Formulations
A Phase 4 study testing Influenza Fluzone vaccine in people with Influenza A, run by La Jolla Institute for Immunology at 1 site in United States.
Trial summary
Every 1-2 years, the seasonal influenza vaccine composition changes to include updated viruses, yet the precise effects of updating the vaccine remain understudied. Since the vaccine formulation for each season (with a season defined as starting in July and ending the following June) expires on June 30, vaccine… Read more about this study
- Who is it for?
- Ages 18 to 64 yearsHealthy volunteers can take part
- Conditions the study is for
- Influenza A
- What is being tested?
- Influenza Fluzone vaccine
- Type of treatment
- Vaccines
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 23 participants
- Where
- 1 siteUnited States
- Study dates
- 21 May 2024to 6 Feb 2025
- Phase
- Phase 4
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 64 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Be between 18-64 years of age
- Males or non-pregnant, non-nursing females
- Weigh at least 85 pounds for whole blood draw
- Ability to provide signed informed consent
- Subjects must plan to receive the intramuscular influenza vaccine at the La Jolla Institute for Immunology
Who cannot join
- Received an influenza vaccine in the past year
- Infection with human immunodeficiency virus, hepatitis B virus, or hepatitis C virus
- History of certain anemias
- Presence of significant cardiovascular disease, systemic diseases including, but not limited to, diabetes which is not controlled, renal disease, liver disease, malignancy, infection, or blood clotting disorder
- Inability to provide informed consent
- Recent whole blood donation within 56 days or leukapheresis within 112 days
Show all 9Show fewer
- Children (under 18 years of age), elderly (65 years of age or older), pregnant or nursing females
- Individuals with egg allergies
- Has ever had Guillain-Barré syndrome
Trial locations and contacts
1 site in 1 country.
United States1 site
La Jolla Institute for Immunology
La Jolla, California, 92037
About this study
Every 1-2 years, the seasonal influenza vaccine composition changes to include updated viruses, yet the precise effects of updating the vaccine remain understudied. Since the vaccine formulation for each season (with a season defined as starting in July and ending the following June) expires on June 30, vaccine formulations cannot be compared head-to-head. Thus, the 2023 and 2024 vaccines have only been compared by analyzing people given the former vaccine in the fall of 2023 and people given the latter vaccine in the fall of 2024, and baseline repertoires may have greatly changed over the course of that year. To that end, the investigators will vaccinate a cohort with the 2023 influenza vaccine between May-June 2024, in order to compare responses between individuals receiving the 2023 vaccine last fall, the 2023 vaccine late in the season (this cohort), and the 2024 vaccine next fall. The investigators will further assess whether the late-season 2023 vaccine primed this cohort to respond better to the standard 2024 vaccine with standard timing (vaccine administered around September-October).
- Conditions
- Influenza A
- Being tested
- Influenza Fluzone vaccine
- Keywords
- Influenza vaccine, Immune response
- Medical subject headings
- Influenza, Human
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Influenza Fluzone vaccineBiological
Fluzone vaccine administered in both May-June and in September-October for each participant.
| Study group | Role | What they receive |
|---|---|---|
| Late season influenza vaccine | Experimental | Every participant receives the 2023 influenza vaccine between May-June 2024, and then the 2024 influenza vaccine in September-October 2024. Blood draws are taken at Day 0, 30, and 90 post-vaccination. Receives: Biological: Influenza Fluzone vaccine |
What is being measured
The primary outcome is the main question the study is designed to answer.
Magnitude of Antibody Response After the Late-season 2023 Vaccine
The antibody response will be measured by hemagglutination inhibition (HAI) in adults between 18 and 64 years old who have not had an influenza vaccination prior to the study.
Measured: 0, 30, and 90 days after the 2023 vaccine
Magnitude of the Antibody Response After the 2024 Vaccine
The antibody response will be measured by hemagglutination inhibition (HAI) in adults between 18 and 64 years old who have not had an influenza vaccination prior to the study. This outcome was only performed on Arm 2.
Measured: Day 0, 30, and 90 after the 2024 vaccine
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted23 Aug 2024
- Study start21 May 2024
- Primary completion6 Feb 2025
- Study completion6 Feb 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for Influenza AStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 4
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 23 participants (actual)
Sponsor and investigators
- Lead sponsor
- La Jolla Institute for Immunology
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Tal Einav, La Jolla Institute for Immunology
- Investigators
- Tal Einav, PhD, Principal investigator, La Jolla Institute for Immunology
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06567860
- Sponsor's protocol ID
- 286
- Status last verified
- Jan 2026
- First submitted
- 20 Aug 2024
- Last updated
- 12 Feb 2026
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: De-identified data will be included in all relevant publications.
Study at a glance
From the registry record, last updated by the sponsor on 12 Feb 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Characterizing Late-season Influenza Vaccine Responses to Compare the 2023 and 2024 Vaccine Formulations
- ClinicalTrials.gov ID
- NCT06567860
- Acronym / sponsor ID
- 286
- Conditions
- Influenza A
- Keywords
- Influenza vaccine, Immune response
- Phase
- Phase 4
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 23 participants (actual)
- Lead sponsor
- La Jolla Institute for ImmunologyUniversity, hospital or other
- Study start
- 21 May 2024 (actual)
- Primary completion
- 6 Feb 2025 (actual)
- Study completion
- 6 Feb 2025 (actual)
- First posted
- 23 Aug 2024 (actual)
- Results
- Posted 12 Feb 2026
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Every 1-2 years, the seasonal influenza vaccine composition changes to include updated viruses, yet the precise effects of updating the vaccine remain understudied. Since the vaccine formulation for each season (with a season defined as starting in July and ending the following June) expires on June 30, vaccine formulations cannot be compared head-to-head. Thus, the 2023 and 2024 vaccines have only been compared by analyzing people given the former vaccine in the fall of 2023 and people given the latter vaccine in the fall of 2024, and baseline repertoires may have greatly changed over the course of that year. To that end, the investigators will vaccinate a cohort with the 2023 influenza vaccine between May-June 2024, in order to compare responses between individuals receiving the 2023 vaccine last fall, the 2023 vaccine late in the season (this cohort), and the 2024 vaccine next fall. The investigators will further assess whether the late-season 2023 vaccine primed this cohort to respond better to the standard 2024 vaccine with standard timing (vaccine administered around September-October).
Study design
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Late season influenza vaccine | Experimental | Biological: Influenza Fluzone vaccineEvery participant receives the 2023 influenza vaccine between May-June 2024, and then the 2024 influenza vaccine in September-October 2024. Blood draws are taken at Day 0, 30, and 90 post-vaccination. |
Who may qualify
- Ages
- 18 to 64 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (5 listed)
- Be between 18-64 years of age
- Males or non-pregnant, non-nursing females
- Weigh at least 85 pounds for whole blood draw
- Ability to provide signed informed consent
- Subjects must plan to receive the intramuscular influenza vaccine at the La Jolla Institute for Immunology
Key exclusion criteria (9 listed)
- Received an influenza vaccine in the past year
- Infection with human immunodeficiency virus, hepatitis B virus, or hepatitis C virus
- History of certain anemias
- Presence of significant cardiovascular disease, systemic diseases including, but not limited to, diabetes which is not controlled, renal disease, liver disease, malignancy, infection, or blood clotting disorder
- Inability to provide informed consent
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Influenza Fluzone vaccineFluzone vaccine administered in both May-June and in September-October for each participant. | Biological | Late season influenza vaccine |
Primary outcome
Magnitude of Antibody Response After the Late-season 2023 Vaccine
Time frame: 0, 30, and 90 days after the 2023 vaccine
The antibody response will be measured by hemagglutination inhibition (HAI) in adults between 18 and 64 years old who have not had an influenza vaccination prior to the study.
Magnitude of the Antibody Response After the 2024 Vaccine
Time frame: Day 0, 30, and 90 after the 2024 vaccine
The antibody response will be measured by hemagglutination inhibition (HAI) in adults between 18 and 64 years old who have not had an influenza vaccination prior to the study. This outcome was only performed on Arm 2.
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 12 Feb 2026.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- Individual participant dataSharing planned: Yes. De-identified data will be included in all relevant publications.
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Healthy Participants
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Tal Einav, PhD principal investigator
La Jolla Institute for Immunology
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 4 study testing Influenza Fluzone vaccine in people with Influenza A, run by La Jolla Institute for Immunology at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 12 Feb 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 4 studies take place after a treatment is approved, to learn more about its long-term benefits and risks in everyday use.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 12 Feb 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Magnitude of Antibody Response After the Late-season 2023 Vaccine (time frame: 0, 30, and 90 days after the 2023 vaccine). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 12 Feb 2026.