NCT04579588 · Stanford University
Understanding Immunity to the Flu Vaccine in COVID-19 Patients
What this study is about
The purpose of this study is to measure immunity to the flu vaccine over time in patients who have had COVID-19 and may have other medical conditions including obesity, type 2 diabetes, chronic fatigue, or long-term COVID-19 symptoms. Adults and children (age 9 to 64) who had been diagnosed with COVID-19 as well as controls without COVID-19 will be invited to participate in this study.
View original scientific description
The purpose of this study is to measure immunity to the flu vaccine over time in patients who have had COVID-19 and may have other medical conditions including obesity, type 2 diabetes, chronic fatigue, or long-term COVID-19 symptoms. Adults and children (age 9 to 64) who had been diagnosed with COVID-19 as well as controls without COVID-19 will be invited to participate in this study.
Interventions
BIOLOGICAL
Flu shot
All participants will receive a single shot of the flu vaccine
Primary outcome measures
Testing immunity to the flu vaccine over time
Time frame: 1 week
Testing immunity to the flu vaccine over time
Time frame: 1 month
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Age 9 through 64 years
- Diagnosed with COVID-19 at least 2 months prior enrollment
- Patients with or without obesity, diabetes, chronic fatigue and/or long term COVID-19 symptoms
- Patients without COVID-19 diagnosis for controls
Exclusion criteria
- Received the influenza vaccine less than 4 months ago
- Pregnant or lactating
- Patients with special risks attendant to venipuncture
- Use of immunomodulatory medications that may impact vaccine immune response per clinician's judgment
- Contraindication to the flu vaccine
- Immunodeficiency or autoimmune disease that may impact vaccine immune responses per clinician's judgement
Where
- Palo Alto, California
Collaborators
National Institute of Allergy and Infectious Diseases (NIAID)
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Mar 18, 2026 · Source of record for eligibility and locations