High vs. Standard Dose Influenza Vaccines in Lung Transplant (Repeater)

The study is a phase II, single-center, double-blind, randomized controlled immunogenicity and safety trial comparing two doses of HD-IIV to two doses of SD-IIV over two consecutive years in lung transplant recipients. At study enrollment, following consent, participants will receive either HD-IIV or SD-IIV , with study arm assignments based on DMID protocol number 22-0014. Therefore, participants will ultimately receive four total doses of either HD-IIV or four total doses of SD-IIV over two consecutive influenza seasons.

• Fluzone High Dose Inactivated Influenza Vaccine (Biological), also known as Fluzone High Dose: Fluzone High-Dose (Influenza Vaccine) for intramuscular use 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 containing hemagglutinin (HA) antigen is further purified and then suspended in sodium phosphate-buffered isotonic sodium chloride solution. The Fluzone High-Dose process uses an additional concentration factor after the ultrafiltration step to obtain a higher HA antigen concentration. The purified split virus from the three strains included in the vaccine are produced separately and then combined to make the trivalent formulation.
• Fluzone Standard Dose Inactivated Influenza Vaccine (Biological), also known as Fluzone: Fluzone Standard Dose is a vaccine indicated for active immunization for the prevention of disease caused by influenza A subtype viruses and type B virus contained in the vaccine.

Primary outcomes

• Immunogenicity: Geometric Mean Titers of Influenza Vaccine Antibodies [Four-eight weeks following the second study vaccination]: HAI GMT to influenza antigens four-eight weeks following the second study vaccination
• Safety - The number of participants reporting solicited injection site reactions [Within 7 days post vaccination]: Solicited Injection-site Adverse Events Following each Vaccination Dose (Pain, Tenderness, Swelling/induration, Erythema/redness)
• Safety - The number of participants reporting systemic adverse events [Within 7 days post vaccination]: Systemic adverse events (Fatigue/malaise, headache, nausea, body ache/myalgia (not at the injection site), general activity level, vomiting, and fever)

Secondary outcomes

• The number of participants achieving seroprotection and seroconversion for influenza virus after receiving either two doses of HD-IIV or two doses of SD-IIV over two consecutive years [Four to eight weeks after vaccination]: 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.
• Geometric Mean Titers of Influenza Vaccine Antibodies after One or Two Doses in the Second Year [Within four to eight weeks post vaccination after 1st and 2nd vaccine]: To quantify and compare the degree to which one versus two doses of either HD-IIV or SD-IIV in the subsequent season elicits enhanced immunogenicity compared to two doses of either HD-IIV or SD-IIV in the first influenza season in lung transplant recipients. Measuring GMT 4-8 weeks after 1st and 2nd vaccine.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Lung transplant recipient who enrolled and completed Visits 1, 2, and 3 of the DMID protocol number 22-0014 during the prior 2024-2025 or 2025-2026 influenza season, respectively

  * Anticipated to be available for the duration of the study
  * Can be reached by telephone, text message, email, or electronic health record messaging

Exclusion Criteria:

* Recipient of multi-organ, extra-pulmonary, and/or hematopoietic stem cell transplant
* Recipient of a re-do lung transplant
* History of Guillain-Barre syndrome
* History of receiving the current season's influenza vaccine prior to study enrollment and/or Visit 1 of this follow-up study
* Pregnant person
* Laboratory-confirmed influenza disease after September 1st in the current influenza season and before enrollment in this follow-up study (patient can still receive the second influenza vaccination despite proven influenza disease after enrollment)
* CMVIG/IVIG/SCIG receipt within 28 days of each vaccine
* Receipt of rituximab or other B-cell depleting antibody (including proteasome inhibitors) therapy within 3 months of 1st vaccine dose (Day 0)
* Receipt of T-cell depleting therapies (anti-thymocyte globulin, alemtuzumab, daratumumab) between the completion of Visit 3 of the initial study and enrollment in this follow-up study
* Investigator concern about study participation
* Note: Criteria for temporarily delaying vaccine administration: The following conditions are temporary or self-limiting, and a participant may be included in the study once the condition has resolved, provided that the participant is otherwise eligible:

  * Fever ≥100.4ºF/38.0ºC (oral measurement), or an acute severe illness within 48 hours of enrollment
  * Receipt of any live vaccines within four weeks or any inactivated vaccines within two weeks prior to potential study vaccination

No children have been enrolled in the DMID protocol number 22-0014; therefore, only adults will be enrolled in this current study

• Natahsa Halasa, MD, MPH, Principal investigator, Vanderbilt University Medical Center