Understanding Immunity to the Flu Vaccine in COVID-19 Patients

March 16, 2026 updated by: Sayantani B. Sindher, Stanford University
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.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Observational

Enrollment (Estimated)

230

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 64 years (Child, Adult)

Accepts Healthy Volunteers

Yes

Sampling Method

Non-Probability Sample

Study Population

Adults (18-64 years) and children (9-17 years) diagnosed and not diagnosed (controls) with COVID-19 and who may have other medical conditions including long term COVID-19 symptoms, chronic fatigue, type 2 diabetes, and obesity.

Description

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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Control participants
Biological: Flu shot
All participants will receive a single shot of the flu vaccine
COVID-19 participants
Biological: Flu shot
All participants will receive a single shot of the flu vaccine

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Testing immunity to the flu vaccine over time
Time Frame: 1 month
1 month
Testing immunity to the flu vaccine over time
Time Frame: 1 week
1 week

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Stanford University

Collaborators

National Institute of Allergy and Infectious Diseases (NIAID)

Investigators

  • Principal Investigator: Sayantani Sindher, MD, Stanford University

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

October 29, 2020

Primary Completion (Estimated)

April 1, 2028

Study Completion (Estimated)

April 1, 2028

Study Registration Dates

First Submitted

October 6, 2020

First Submitted That Met QC Criteria

October 6, 2020

First Posted (Actual)

October 8, 2020

Study Record Updates

Last Update Posted (Actual)

March 18, 2026

Last Update Submitted That Met QC Criteria

March 16, 2026

Last Verified

November 1, 2025

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • IRB-58356
  • 5U19AI057229-17 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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