InfluenzaNCT06029933
Fluad vs. Fluzone High-Dose Vaccine Effectiveness Among Adults ≥65 Years
An observational study of Influenza and Community-acquired Pneumonia, run by Kaiser Permanente at 1 site in United States.
Trial summary
This study will evaluate the relative vaccine effectiveness of quadrivalent adjuvanted inactivated influenza vaccine (aIIV4) versus quadrivalent high-dose inactivated influenza vaccine (HD-IIV4) in preventing polymerase chain reaction (PCR)-confirmed influenza and influenza-related outcomes in adults ≥65 years of age… Read more about this study
- Who is it for?
- Ages 65 years and olderHealthy volunteers can take part
- Conditions the study is for
- Influenza, Community-acquired Pneumonia, Cardiovascular Events
- What is being tested?
- Adjuvanted Quadrivalent Inactivated Influenza Vaccine (aIIV4) and High-Dose Quadrivalent Inactivated Influenza Vaccine (HD-IIV4)
- Type of treatment
- Vaccines
- How many people
- 1,500,000 participants
- Where
- 1 siteUnited States
- Study dates
- 17 Aug 2023to May 2028
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
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 65 years and older
- All sexes
- Healthy volunteers accepted
- Older adult
Study population: This study includes KPNC adults ≥65 years who receive Fluad or Fluzone High-Dose influenza vaccine as part of routine clinical care during the 2023/24, 2024/25, and/or 2026/27 influenza seasons.
Who may be able to join
- Age ≥65 years at the time of influenza vaccination
- KPNC member at the time of vaccination
- Receive either aIIV4 or HD-IIV4 at a KPNC facility during the 2023/24 and/or 2024/25 influenza seasons
Who cannot join
- Age <65 years at the time of influenza vaccination
- Received either aIIV4 or HD-IIV4 in the inpatient setting
- Receive more than one influenza vaccination during a single season period (i.e., 2023/24 or 2024/25 influenza seasons)
- Receive an influenza vaccination outside of KPNC
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
Kaiser Permanente Northern California (entire region)
Oakland, California, 94612
Amber H. Hyman, PhD, MPH, (510) 267-7517, Amber.Hyman@kp.org
Nicola P. Klein, MD, PhD
About this study
Official title: Relative Vaccine Effectiveness of Adjuvanted Inactivated Influenza Vaccine (aIIV) vs High-Dose Inactivated Influenza Vaccine (HD-IIV) for Prevention of Lab-Confirmed Influenza Among Adults ≥65 Years of Age in the United States
This study will evaluate the relative vaccine effectiveness of quadrivalent adjuvanted inactivated influenza vaccine (aIIV4) versus quadrivalent high-dose inactivated influenza vaccine (HD-IIV4) in preventing polymerase chain reaction (PCR)-confirmed influenza and influenza-related outcomes in adults ≥65 years of age during the 2023/24, 2024/25, and 2026/27 influenza seasons. The study is an observational study conducted at Kaiser Permanente Northern California (KPNC), an integrated health care system in the United States.
- Being tested
- Adjuvanted Quadrivalent Inactivated Influenza Vaccine (aIIV4), High-Dose Quadrivalent Inactivated Influenza Vaccine (HD-IIV4)
- Medical subject headings
- Influenza, Human, Community-Acquired Pneumonia
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Adjuvanted Quadrivalent Inactivated Influenza Vaccine (aIIV4)Biological
Also called Fluad
Fluad Quadrivalent vaccine is an inactivated influenza vaccine formulated to contain 60 mcg of hemagglutinin (HA) total, with 15 mcg from each of the four recommended influenza strains and the MF59 adjuvant in single-dose prefilled 0.5 mL syringes. Kaiser Permanente Northern California members ≥65 years may receive Fluad as part of routine clinical care during the influenza season.
High-Dose Quadrivalent Inactivated Influenza Vaccine (HD-IIV4)Biological
Also called Fluzone High-Dose
Fluzone High-Dose Quadrivalent vaccine is an inactivated split virion influenza vaccine formulated to contain 240 mcg of HA total, with 60 mcg from each of the four recommended influenza strains in single-dose prefilled 0.7 mL syringes. Kaiser Permanente Northern California members ≥65 years may receive Fluzone High-Dose as part of routine clinical care during the influenza season.
| Study group | Role | What they receive |
|---|---|---|
| Fluad Recipients | Kaiser Permanente Northern California members aged ≥65 years who receive Adjuvanted Quadrivalent Inactivated Influenza Vaccine (aIIV4) Receives: Biological: Adjuvanted Quadrivalent Inactivated Influenza Vaccine (aIIV4) | |
| Fluzone High-Dose Recipients | Kaiser Permanente Northern California members aged ≥65 years who receive High-Dose Quadrivalent Inactivated Influenza Vaccine (HD-IIV4) Receives: Biological: High-Dose Quadrivalent Inactivated Influenza Vaccine (HD-IIV4) |
What is being measured
The primary outcome is the main question the study is designed to answer.
PCR-confirmed influenza
KPNC members ≥65 years who receive Fluad or Fluzone High-Dose will be retrospectively assessed for the presence of PCR-confirmed influenza. This outcome will be assessed in single-season analyses (2023/24, 2024/25, and 2026/27 separately) and a pooled analysis across all seasons.
Measured: ≥14 days after vaccination until date of outcome, death, loss-to-follow-up, or end of each season (estimated May 2024, May 2025, or May 2027)
Secondary outcomes (3)
Emergency department visit or hospitalization for PCR-confirmed influenza
KPNC members ≥65 years who receive Fluad or Fluzone High-Dose will be retrospectively assessed for an emergency department visit or hospitalization for PCR-confirmed influenza. This outcome will be assessed in single-season analyses (2023/24, 2024/25, and 2026/27 separately) and a pooled analysis across all seasons combined.
Measured: ≥14 days after vaccination until date of outcome, death, loss-to-follow-up, or end of each season (estimated May 2024, May 2025, or May 2027)
Hospitalization for PCR-confirmed influenza
KPNC members ≥65 years who receive Fluad or Fluzone High-Dose will be retrospectively assessed for hospitalization for PCR-confirmed influenza. This outcome will be assessed in a pooled analysis across all seasons combined.
Measured: ≥14 days after vaccination until date of outcome, death, loss-to-follow-up, or end of each season (estimated May 2024, May 2025, or May 2027)
Hospitalization for all-cause community-acquired pneumonia
KPNC members ≥65 years who receive Fluad or Fluzone High-Dose will be retrospectively assessed for hospitalization for all-cause community-acquired pneumonia. This outcome will be assessed in single-season analyses (2023/24, 2024/25, and 2026/27 separately) and a pooled analysis across all seasons combined.
Measured: ≥14 days after vaccination until date of outcome, death, loss-to-follow-up, or end of each season (estimated May 2024, May 2025, or May 2027)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted8 Sep 2023
- Study start17 Aug 2023
- Primary completionMay 2027 (estimated)
- Study completionMay 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for InfluenzaStudies 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
- Observational
- Observational model
- Cohort
- Time perspective
- Retrospective
- Enrolment
- 1,500,000 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Kaiser Permanente
- Sponsor type
- University, hospital or other
- Collaborators
- Seqirus
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06029933
- Sponsor's protocol ID
- 2033496
- Status last verified
- Jul 2026
- First submitted
- 28 Aug 2023
- Last updated
- 5 Aug 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Hsiao A, Leong T, Fireman B, Hansen J, Zerbo O, Jacobson KB, Liao LD, Haag MDM, McGovern I, Zhang B, Dang J, Klein NP. Adjuvanted vs High-Dose Influenza Vaccines in Older US Adults: A Cluster Randomized Crossover Study. JAMA Netw Open. 2026 May 1;9(5):e2610120. doi: 10.1001/jamanetworkopen.2026.10120.
PubMed 42081247
Study at a glance
From the registry record, last updated by the sponsor on 5 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Relative Vaccine Effectiveness of Adjuvanted Inactivated Influenza Vaccine (aIIV) vs High-Dose Inactivated Influenza Vaccine (HD-IIV) for Prevention of Lab-Confirmed Influenza Among Adults ≥65 Years of Age in the United States
- ClinicalTrials.gov ID
- NCT06029933
- Acronym / sponsor ID
- 2033496
- Study type
- Observational
- Recruitment status
- Recruiting
- Enrolment
- 1,500,000 participants (estimated)
- Lead sponsor
- Kaiser PermanenteUniversity, hospital or other
- Collaborators
- Seqirus
- Study start
- 17 Aug 2023 (actual)
- Primary completion
- May 2027 (estimated)
- Study completion
- May 2028 (estimated)
- First posted
- 8 Sep 2023 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study will evaluate the relative vaccine effectiveness of quadrivalent adjuvanted inactivated influenza vaccine (aIIV4) versus quadrivalent high-dose inactivated influenza vaccine (HD-IIV4) in preventing polymerase chain reaction (PCR)-confirmed influenza and influenza-related outcomes in adults ≥65 years of age during the 2023/24, 2024/25, and 2026/27 influenza seasons. The study is an observational study conducted at Kaiser Permanente Northern California (KPNC), an integrated health care system in the United States.
Study design
- Observational model
- Cohort
- Time perspective
- Retrospective
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Fluad Recipients | – | Biological: Adjuvanted Quadrivalent Inactivated Influenza Vaccine (aIIV4)Kaiser Permanente Northern California members aged ≥65 years who receive Adjuvanted Quadrivalent Inactivated Influenza Vaccine (aIIV4) |
| Fluzone High-Dose Recipients | – | Biological: High-Dose Quadrivalent Inactivated Influenza Vaccine (HD-IIV4)Kaiser Permanente Northern California members aged ≥65 years who receive High-Dose Quadrivalent Inactivated Influenza Vaccine (HD-IIV4) |
Who may qualify
- Ages
- 65 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Older adult
- Study population
- This study includes KPNC adults ≥65 years who receive Fluad or Fluzone High-Dose influenza vaccine as part of routine clinical care during the 2023/24, 2024/25, and/or 2026/27 influenza seasons.
Key inclusion criteria (3 listed)
- Age ≥65 years at the time of influenza vaccination
- KPNC member at the time of vaccination
- Receive either aIIV4 or HD-IIV4 at a KPNC facility during the 2023/24 and/or 2024/25 influenza seasons
Key exclusion criteria (4 listed)
- Age <65 years at the time of influenza vaccination
- Received either aIIV4 or HD-IIV4 in the inpatient setting
- Receive more than one influenza vaccination during a single season period (i.e., 2023/24 or 2024/25 influenza seasons)
- Receive an influenza vaccination outside of KPNC
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 |
|---|---|---|
| Adjuvanted Quadrivalent Inactivated Influenza Vaccine (aIIV4)Also: FluadFluad Quadrivalent vaccine is an inactivated influenza vaccine formulated to contain 60 mcg of hemagglutinin (HA) total, with 15 mcg from each of the four recommended influenza strains and the MF59 adjuvant in single-dose prefilled 0.5 mL syringes. Kaiser Permanente Northern California members ≥65 years may receive Fluad as part of routine clinical care during the influenza season. | Biological | Fluad Recipients |
| High-Dose Quadrivalent Inactivated Influenza Vaccine (HD-IIV4)Also: Fluzone High-DoseFluzone High-Dose Quadrivalent vaccine is an inactivated split virion influenza vaccine formulated to contain 240 mcg of HA total, with 60 mcg from each of the four recommended influenza strains in single-dose prefilled 0.7 mL syringes. Kaiser Permanente Northern California members ≥65 years may receive Fluzone High-Dose as part of routine clinical care during the influenza season. | Biological | Fluzone High-Dose Recipients |
Primary outcome
PCR-confirmed influenza
Time frame: ≥14 days after vaccination until date of outcome, death, loss-to-follow-up, or end of each season (estimated May 2024, May 2025, or May 2027)
KPNC members ≥65 years who receive Fluad or Fluzone High-Dose will be retrospectively assessed for the presence of PCR-confirmed influenza. This outcome will be assessed in single-season analyses (2023/24, 2024/25, and 2026/27 separately) and a pooled analysis across all seasons.
3 secondary outcomes
Emergency department visit or hospitalization for PCR-confirmed influenza
Time frame: ≥14 days after vaccination until date of outcome, death, loss-to-follow-up, or end of each season (estimated May 2024, May 2025, or May 2027)
Hospitalization for PCR-confirmed influenza
Time frame: ≥14 days after vaccination until date of outcome, death, loss-to-follow-up, or end of each season (estimated May 2024, May 2025, or May 2027)
Hospitalization for all-cause community-acquired pneumonia
Time frame: ≥14 days after vaccination until date of outcome, death, loss-to-follow-up, or end of each season (estimated May 2024, May 2025, or May 2027)
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 5 Aug 2026.
- Derived from this study: PubMed 42081247Hsiao A, Leong T, Fireman B, Hansen J, Zerbo O, Jacobson KB, Liao LD, Haag MDM, McGovern I, Zhang B, Dang J, Klein NP. Adjuvanted vs High-Dose Influenza Vaccines in Older US Adults: A Cluster Randomized Crossover Study. JAMA Netw Open. 2026 May 1;9(5):e2610120. doi: 10.1001/jamanetworkopen.2026.10120.
- Individual participant dataSharing planned: No
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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.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Influenza and Community-acquired Pneumonia, run by Kaiser Permanente 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 3 inclusion and 4 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: looking for participants now, as of the sponsor's last update on 5 Aug 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.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Amber H. Hyman, PhD, MPH (510-267-7571, Amber.Hyman@kp.org), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
PCR-confirmed influenza (time frame: ≥14 days after vaccination until date of outcome, death, loss-to-follow-up, or end of each season (estimated May 2024, May 2025, or May 2027)). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT06029933, which also lists 1 linked publication.
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 5 Aug 2026; AzTrials last refreshed its copy on 26 Oct 2026.