Fluad vs. Fluzone High-Dose Vaccine Effectiveness Among Adults ≥65 Years
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
Who can join
Ages 65 and older · All sexes · Healthy volunteers welcome
Full eligibility criteria
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
About the study
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.
What is being tested
- Adjuvanted Quadrivalent Inactivated Influenza Vaccine (aIIV4) (biological)
- High-Dose Quadrivalent Inactivated Influenza Vaccine (HD-IIV4) (biological)
Sponsor: Kaiser Permanente · Participants: 1,500,000 · Started: Aug 17, 2023
Contact the study team
- Amber H. Hyman, PhD, MPH · Phone: 510-267-7571
Official record on ClinicalTrials.gov — NCT06029933
Locations in the U.S.
| California | Kaiser Permanente Northern California (entire region), Oakland |
Conditions
From ClinicalTrials.gov, data retrieved Sep 30, 2026. Each study sets its own eligibility; the study team decides who can join.