A Phase 2 interventional study of Standard Dose Quadrivalent Inactivated Influenza Vaccine and High Dose Quadrivalent Inactivated Influenza Vaccine in Immunization; Infection, Transplantation Infection and Influenza, sponsored by National Institute of Allergy and Infectious Diseases (NIAID). Recruiting at 11 sites in United States. Open to participants aged 3 Years to 17 Years. Per ClinicalTrials.gov, last updated 2026-10-28.
Sponsored by National Institute of Allergy and Infectious Diseases (NIAID) · Phase 2, Interventional, and Prevention
Influenza virus is a significant pathogen in pediatric solid organ transplant (SOT) recipients. However, these individuals respond poorly to standard-dose (SD) inactivated influenza vaccine (IIV). Recent studies have investigated two strategies to overcome poor immune responses in SOT recipients: (1) administration of high-dose (HD)-IIV compared to SD-IIV and (2) two doses of SD-IIV compared to one dose of SD-IIV in the same influenza season. One study compared HD-IIV vs. SD-IIV in adult SOT recipients and noted that HD-IIV was safe and more immunogenic; however, the median post-transplant period was 38 months. A phase I pediatric study comparing a single dose of HD-IIV vs. SD-IIV was safe with higher immunogenicity, but the study was limited by small sample size and median post-transplant vaccine administration was 26 months. In another phase II trial of adult SOT recipients, two doses of SD-IIV one month apart compared to one-dose of SD-IIV revealed modestly increased immunogenicity when given at a median of 18 months post-transplant. Therefore, these studies lack both evaluation in the early post-transplant period and substantive pediatric populations. Additionally, the administration of two-doses of HD-IIV in the same influenza season has not been evaluated in pediatric SOT recipients. Thus, the optimal immunization strategy for pediatric SOT recipients less than 24 months post-transplant is unknown. In addition, immunologic predictors and correlates of influenza vaccine immunogenicity in pediatric SOT recipients have not been well-defined.
The central hypothesis of our proposal is that pediatric SOT recipients 1-23 months post-transplant who receive two doses of HD-quadrivalent inactivated influenza vaccine (QIV) will have similar safety but higher Hemagglutination Inhibition (HAI) geometric mean titers (GMTs) to influenza antigens compared to pediatric SOT recipients receiving two doses of SD-QIV.
Study design: This is a phase II, multi-center, double-blind, randomized controlled immunogenicity and safety trial comparing two doses of HD-QIV or two doses of SD-QIV in pediatric SOT recipients.
Hypotheses:
Study population: The study plans to enroll a total of approximately 312 pediatric heart, liver, and/or kidney transplant recipients between 1 and 23 months post-transplantation.
Study enrollment: The enrollment period will be over three-years. Participants will be randomized into one of two groups. Group 1 will receive two doses of SD-QIV (0.5 mL; 15μg of each influenza antigen) whereas Group 2 will receive two doses HD-QIV (0.7 mL; 60μg of each influenza antigen).
Influenza surveillance: Active surveillance for influenza-like symptoms will begin when influenza season starts in each site's community, defined in previous trials as identification of at least two positive respiratory tests for influenza, with at least 10% of diagnostic tests positive during two consecutive weeks in the local clinical or research laboratory. Enrollment will continue during influenza season with nasal swabs obtained at all main visits to document the occurrence of influenza virus both prior to and after vaccination. During the influenza season, the study staff will attempt to do a weekly telephone and/or electronic communication with the participants to detect and document any influenza-like illness (ILI) and any specific coronavirus disease of 2019 (COVID-19) like symptoms.
If participants meet ILI criteria and/or any specific coronavirus disease of 2019 (COVID-19) like symptoms (see below), an additional nasal swab will be collected*.
ILI criteria are met by occurrence of one of the conditions below:
Two or more of any of the following: respiratory symptoms (rhinorrhea, sinus congestion, post-nasal drip, shortness of breath, cough, wheezing, sputum production, sore throat, sneezing, watery eyes, ear pain, hoarseness); or systemic symptoms (myalgias, chills, chest pain, or headache); or new loss of taste or new loss of smell; or gastrointestinal symptoms (diarrhea or vomiting).
2,356 studies on the registry are indexed under Influenza, Human; 184 are open to participants now.
This study's planned enrollment of 312 is above the median of 227 across 1,957 interventional studies indexed under Influenza, Human.
Browse Influenza, Human studies →National Institute of Allergy and Infectious Diseases (NIAID) is the lead sponsor of 2,446 studies on the registry; 179 are open to participants now.
Of its 405 completed or terminated interventional studies of FDA-regulated products, 302 (75%) have results posted.
Compared within Influenza, Human, this study's primary condition as ClinicalTrials.gg classifies it; the registry's first condition term is Infections. The counts are of registry records indexed under each term, refreshed daily. How we classify →
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Pediatric kidney, heart, and/or liver transplant recipient ≥1 month and \<24 months post-transplant at the time of study immunization
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Two doses of SD-QIV (0.5 mL; 15µg of each influenza antigen) 28-42 days apart
Biological: Standard Dose Quadrivalent Inactivated Influenza Vaccine
Two doses of HD-QIV (0.7 mL; 60µg of each influenza antigen) 28-42 days apart
Biological: High Dose Quadrivalent Inactivated Influenza Vaccine
Fluzone ® Quadrivalent is a vaccine indicated for active immunization for the prevention of influenza disease caused by two influenza A subtype viruses and two type B viruses contained in the vaccine.
Also known as: Fluzone
Fluzone High-Dose (Influenza Vaccine) for intramuscular injection is an inactivated influenza vaccine, prepared from influenza viruses propagated in embryonated chicken eggs. The virus-containing allantoic fluid is harvested and inactivated with formaldehyde. Influenza virus is concentrated and purified in a linear sucrose density gradient solution using a continuous flow centrifuge. The virus is then chemically disrupted using a non-ionic surfactant, octylphenol ethoxylate (Triton® X-100), producing a "split virus". The split virus is further purified and then suspended in sodium phosphatebuffered isotonic sodium chloride solution. The Fluzone High-Dose process uses an additional concentration factor after the ultrafiltration step in order to obtain a higher hemagglutinin (HA) antigen concentration.
Also known as: Fluzone High Dose
Immunogenicity: Hemagglutination Inhibition (HAI) titers
Antibody titers will be measured by hemagglutination inhibition assay.
Time frame: 4 weeks following the 2nd study vaccine
Safety: solicited local and systemic post-administration reactions
Post-vaccination local adverse events (pain, tenderness, swelling/induration, erythema/redness, swelling/induration size, and erythema/redness size) and systemic adverse events (Fatigue/malaise, headache, nausea, body ache/myalgia (not at the injection site), general activity level, vomiting, and fever).
Time frame: in the first 7 days following each study vaccine
Immunogenicity: Hemagglutination Inhibition (HAI) titers
Antibody titers will be measured by hemagglutination inhibition assay.
Time frame: 4 weeks following 1st and 2nd doses of each study vaccine
The number of participants achieving seroprotection and seroconversion for influenza virus.
Antibody titers will be measured by hemagglutination inhibition assay. Seroconversion is defined as ≥ 4-fold rise in hemagglutination inhibition assay titers. Seroprotection is defined as ≥1:40 hemagglutination inhibition assay titer.
Time frame: 4 weeks following the 1st and 2nd study vaccination
Durability of immunogenicity
Measured as Hemagglutination Inhibition (HAI) titer at end of season
Time frame: 180 days after vaccine 2
Plan to share: No
No publications or documents are linked to this record.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
No contact was published for this record. The registry link below has the sponsor’s details.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
National Institute of Allergy and Infectious Diseases (NIAID) →