A Pragmatic Assessment of Influenza Vaccine Effectiveness in the DoD
Influenza · Influenza-like Illness · Influenza Vaccines
What this study involves
The registry does not currently label this study as recruiting. Ask about its status before planning a screening visit.
- Study type
- Interventional
- Phase
- Phase 4
- Age range
- 18 years - Not specified
- Sex eligible
- All sexes
- Healthy volunteers
- Accepted
- Participants
- 15448 Actual
These are starting points, not an eligibility decision. The research team must review the full requirements.
About the research
A total of 18,000 eligible subjects (or 6,000 subject distributed evenly between the 3 study arms) will be enrolled. Eligible subjects will be randomized in 1:1:1 (cell-culture-based vaccine, the recombinant vaccine, or the egg-based vaccine) over four influenza seasons (2018-2019, 2019-2020, 2020-2021, and 2021-2022).
Read the full description
This four-year, pragmatic, prospective study will compare the effectiveness of licensed egg-based inactivated influenza vaccines to the effectiveness of two other types of licensed vaccines, the cell-culture based inactivated influenza vaccine and the recombinant influenza vaccine, in the prevention of laboratory-confirmed influenza infection in active duty members, military retirees, and other DoD beneficiaries. Military treatment facilities (MTFs) in the United States will participate in this protocol. Enrollment will be restricted to adults (≥18 years and older) who are preparing to receive seasonal influenza vaccination at participating DoD sites. Subjects will be randomized to receive one of the three licensed influenza vaccines types for evaluation of effectiveness. There is no exclusion for pregnancy, as none of these licensed products are contraindicated in pregnant women.
Who may be able to participate?
The list below is the sponsor’s full registry wording. It can include conditions, prior treatment, test results and other requirements. A match in search does not mean you qualify.
Inclusion Criteria:
1. Eligible for care in Department of Defense medical facilities (Defense Enrollment Eligibility Reporting System eligible)
2. ≥18 years of age.
3. At a participating Military Treatment Facility site for the purpose of receiving a seasonal (2018-2019, 2019-2020,2020-2021, 2021-2022) influenza vaccination.
4. Able to speak English and able to provide informed consent
5. Able to receive and respond to texts and/or emails, or a military recruit
Exclusion Criteria:
1. Adults intending to receive or who have received the current seasons FluMist Vaccine (LAIV)
2. Adults who have already received a flu vaccine within the current season
3. Individual who cannot receive a flu vaccine or standard dosing due to another medical condition
4. Allergic to gentamicin, polymyxin and/or neomycin
5. Individuals who fail to meet the inclusion criteria
Treatment, groups and participation
The registry may describe treatments and study duration without a complete visit calendar. Ask the study team for the exact schedule, procedures, risks, costs and alternatives. Keep your usual care plan unless your treating clinician tells you otherwise.
- Assignment
- Random assignment
- Masking
- No masking
Egg based influenza vaccines
Quadrivalent egg-based vaccines, which contain an inactivated form of the virus. Vaccines will be given to the participant in accordance with standard clinical practices for those in the US military. All egg-based vaccines are FDA licensed for use in the United States.
Biological: Egg based influenza vaccines
Recombinant influenza vaccines
FluBlok, recombinant HA influenza vaccine. Vaccines will be given to the participant in accordance with standard clinical practices for those in the US military. Flublok Quadrivalent is a quadrivalent recombinant influenza vaccine that has been licensed by the FDA for use in the United States.
Biological: Recombinant influenza vaccines
Cell-culture based influenza vaccines
Flucelvax, Madin-Darby canine kidney (MDCK)-cell-culture based inactivated influenza vaccine. Vaccines will be given to the participant in accordance with standard clinical practices for those in the US military. Flucelvax quadrivalent, the only cell-based flu vaccine FDA licensed for use in the United States.
Biological: Cell-culture based influenza vaccines
Egg based influenza vaccines BIOLOGICAL
Participants will be randomly allocated to one of three vaccine types in accordance with standard clinical practices for those in the US military. All vaccines are FDA licensed for use in the United States.
Recombinant influenza vaccines BIOLOGICAL
Participants will be randomly allocated to one of three vaccine types in accordance with standard clinical practices for those in the US military. All vaccines are FDA licensed for use in the United States.
Cell-culture based influenza vaccines BIOLOGICAL
Participants will be randomly allocated to one of three vaccine types in accordance with standard clinical practices for those in the US military. All vaccines are FDA licensed for use in the United States.
What researchers are measuring
Outcome measures describe what is being studied. They are not proof that a treatment works.
Primary measures
Number of Participants With Laboratory Confirmed Influenza
Time frame: Onset > 13 days after vaccination up to 1 year
Laboratory-confirmed influenza as ascertained by a sensitive and specific assay.
Secondary measures
Hemagglutination Inhibition (HI) Titer Responses to Influenza Vaccine Strains.
Time frame: Baseline to 21-35 days post vaccine
Strain-specific seroconversion rate determined by reference hemagglutination inhibition assay.
Pseudovirion Neutralization (PVN) Responses to Influenza Vaccine.
Time frame: Baseline to 21-35 days post vaccine
Neutralizing antibody responses (4-fold rise) to HA-psuedoviruses corresponding to vaccine-matched viruses, recently circulating influenza virus, and emerging influenza strain.
Anti-Neuraminidase (Anti-NA) Titer Responses to Influenza Vaccine.
Time frame: Baseline to 21-35 days post vaccine
Anti-Neuraminidase (Anti-NA) titer responses determined by enzyme linked immuno-assay.
Number of Participants With Influenza-Like Illness
Time frame: Onset > 13 days after vaccination up to 1 year
Rate of protocol defined influenza-like illness ascertained by participant response to active surveillance.
Other measures
Number of Participants With SARS-CoV-2 and Influenza Co-Infection
Time frame: Onset > 13 days after influenza vaccination up until one year
Laboratory-confirmed SARS CoV2, and SARS CoV2 plus influenza co-infection, as ascertained by nasal swab PCR.
Symptom Severity of SARS CoV2
Time frame: onset >13 days after Influenza vaccination up to 1 year
Symptom severity scores were reported by participants using FLU-PRO Plus (Influenza Patient Reported Outcomes), a standardized instrument developed to measure the intensity and frequency of viral respiratory tract symptoms. FluPRO Plus symptom scores range from 0 ("not at all") to 4 ("very much"), with higher scores indicating greater severity.
Review the complete result tables and limitations in the official record.
Open official results ↗Research locations (9)
The overall study status and a local site’s status can differ. Confirm that location’s availability before traveling.
9 locations
Naval Medical Center San DiegoSan Diego, California, United StatesStatus unknown
United States Naval AcademyAnnapolis, Maryland, United StatesStatus unknown
USUBethesda, Maryland, United StatesStatus unknown
Walter Reed National Military Medical CenterBethesda, Maryland, United StatesStatus unknown
Womack Army Medical CenterFort Bragg, North Carolina, United StatesStatus unknown
Brooke Army Medical CenterFort Sam Houston, Texas, United StatesStatus unknown
Lackland Airforce BaseSan Antonio, Texas, United StatesStatus unknown
Naval Medical Center PortsmouthPortsmouth, Virginia, United StatesStatus unknown
Madigan Army Medical CenterTacoma, Washington, United StatesStatus unknown
Study team and timeline
- Lead sponsor
- Henry M. Jackson Foundation for the Advancement of Military Medicine
- Study start
- Nov 6, 2018 Actual
- Primary completion
- Jul 7, 2022 Actual
- Study completion
- Jun 30, 2026 Actual
- First posted
- Nov 7, 2018 Actual
- Last updated
- Nov 10, 2026 Actual
Official study contacts
No central contact is listed. Check the locations and the official record.
Official study title
A Pragmatic Assessment of Influenza Vaccine Effectiveness in the DoD
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Source: ClinicalTrials.gov API v2. Information is submitted by sponsors and investigators. NLM does not approve the safety or science of all listed studies. Registry disclaimer.
Retrieved: Nov 12, 2026 · Last registry update: Nov 10, 2026