Recruiting

aIIV4 vs. HD-IIV4

Sponsor:

Kaiser Permanente

Code:

NCT06029933

Conditions

Influenza

Community-acquired Pneumonia

Cardiovascular Events

Eligibility Criteria

Sex: All

Age: 65+

Healthy Volunteers: Accepted

Interventions

Adjuvanted Quadrivalent Inactivated Influenza Vaccine (aIIV4)

High-Dose Quadrivalent Inactivated Influenza Vaccine (HD-IIV4)

Study Details

Brief 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 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.

Conditions

Influenza

Community-acquired Pneumonia

Cardiovascular Events

Study ID

NCT06029933

Start date

Aug 17, 2023

Status verified date

Jul, 2026

Completion date

May, 2028

Anticipated

Primary completion date

May, 2027

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 65+

Healthy Volunteers: Accepted

Inclusion Criteria:

  • 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

Exclusion Criteria:

  • 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

Study Design

Enrollment

1500000 participants

Anticipated

Interventions and Outcome Measures

Arms

Fluad Recipients

Kaiser Permanente Northern California members aged ≥65 years who receive 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)

Interventions

Adjuvanted Quadrivalent Inactivated Influenza Vaccine (aIIV4)

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)

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.

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) ]

Central Contacts and Locations

Central contacts

Amber H. Hyman, PhD, MPH

510-267-7571Amber.Hyman@kp.org

Locations

Kaiser Permanente Northern California (entire region)

Recruiting

Oakland, California, United States, 94612

Contacts

Amber H. Hyman, PhD, MPH

(510) 267-7517Amber.Hyman@kp.org

Principal Investigator:

Nicola P. Klein, MD, PhD

More Information

Sponsor

Kaiser Permanente

Last update posted

Aug 5, 2026

Last verified

Jul, 2026

Trial information was received from ClinicalTrials.gov and was last updated on 2026-10-03. This information was provided to ClinicalTrials.gov by Kaiser Permanente on 2026-08-05. Recruitment status is synced daily from ClinicalTrials.gov and may not reflect the sponsor's current status. Confirm during your call.