Study to Evaluate the Safety and the Immunogenicity of a Second Generation Structurally Designed mRNA Vaccine Candidate Against Pandemic Influenza H5 HA Strain in Healthy Adult Participants Aged 18 Years and Older

Recruitment Status
ACTIVE, NOT RECRUITING
(See Contacts and Locations)Verified December 2025 by Sanofi
Sponsor
Sanofi
Information Provided by (Responsible Party)
Sanofi
Clinicaltrials.gov Identifier
NCT06907511
Other Study ID Numbers:
VBS00002
First Submitted
March 25, 2025
First Posted
April 1, 2025
Last Update Posted
January 15, 2026
Last Verified
December 2025

ClinicalTrials.gov processed this data on January 2026. Link to the current ClinicalTrials.gov record .

History of Changes

Study Details

Study Description

Condition or DiseaseIntervention/Treatment
Pandemic Influenza ImmunizationHealthy Volunteers
Biological: Pandemic flu H5 HA mRNA SD2 vaccineBiological: Pandemic flu H5 HA mRNA SD2 vaccineBiological: Pandemic flu H5 HA mRNA SD2 vaccineOther: Placebo

Study Design

Study TypeInterventional
Actual Enrollment720 participants
Design AllocationRandomized
Interventional ModelParallel Assignment
MaskingQuadruple
Primary PurposePrevention
Official TitleA Phase 1/2, Parallel-group, Randomized, Modified Double-blind, Placebo-controlled, Multi-center, Dose Ranging Study to Evaluate the Safety and Immunogenicity of a Second Generation Structurally Designed Pandemic Influenza H5 HA mRNA Vaccine in Healthy Adults Aged 18 Years and Older
Study Start DateApril 16, 2025
Actual Primary Completion Date6mos 3w from now
Actual Study Completion Date6mos 3w from now

Groups and Cohorts

Group/CohortIntervention/Treatment
Group 1: Pandemic flu H5 HA mRNA SD2 vaccine (Low dose)
Participants will receive two injections of low dose pandemic flu H5 HA mRNA SD2 vaccine Extension Phase: Additional participants will receive two injections 21 days apart of pandemic flu H5 HA mRNA SD2 vaccine at low dose
Biological: Pandemic flu H5 HA mRNA SD2 vaccine
Pharmaceutical Form: Suspension in a vial Route of Administration: Intramuscular injection
Group 2: Pandemic flu H5 HA mRNA SD2 vaccine (Medium dose)
Participants will receive two injections of medium dose pandemic flu H5 HA mRNA SD2 vaccine
Biological: Pandemic flu H5 HA mRNA SD2 vaccine
Pharmaceutical Form: Suspension in a vial Route of Administration: Intramuscular injection
Group 3: Pandemic flu H5 HA mRNA SD2 vaccine (High dose)
Participants will receive two injections of high dose pandemic flu H5 HA mRNA SD2 vaccine
Biological: Pandemic flu H5 HA mRNA SD2 vaccine
Pharmaceutical Form: Suspension in a vial Route of Administration: Intramuscular injection
Group 4: Placebo
Participants will receive two injections of placebo Extension Phase: Additional participants will receive two injections 21 days apart of placebo
Other: Placebo
Pharmaceutical Form: Liquid solution in a vial Route of Administration: Intramuscular injection

Outcome Measures

Primary Outcome Measures
  1. Presence of immediate adverse events (AEs)
    Number of participants with immediate AEs
  2. Presence of solicited injection site reactions
    Number of participants with solicited injection site reactions
  3. Presence of solicited systemic reactions
    Number of participants with solicited systemic reactions
  4. Presence of unsolicited AEs
    Number of participants with unsolicited AEs
  5. Presence of medically attended adverse events (MAAEs)
    Number of participants with MAAEs
  6. Presence of adverse events of special interest (AESIs)
    Number of participants with AESIs
  7. Presence of serious adverse events (SAEs)
    Number of participants with SAEs
  8. Presence of out-of-range biological test results (including shift from baseline values)
    Number of participants with out-of-range biological test results
Secondary Outcome Measures
  1. Geometric mean titers (GMTs) of antibodies (Abs) against investigational pandemic flu H5 HA mRNA SD2 vaccine
    Ab titer measured by hemagglutination inhibition (HAI) assay
  2. Individual HA titer ratio
    Geometric mean ratio (GMR) HAI titers ratio
  3. Seroconversion HAI Titer
    Percentage of participants with seroconversion Seroconversion is defined by: HAI titer \< 10 \[1/dilution (dil)\] on Day 01 and post-injection titer ≥ 40 \[1/dil\] on Day 22 or Day 43; or defined as HAI titer ≥ 10 \[1/dil\] on D01 and a ≥ 4-fold increase in titer \[1/dil\]) on Day 22 or Day 43
  4. HAI titer ≥ 40 (1/dil)
    Percentage of participants with HAI titer ≥ 40 (1/dil)
  5. Detectable HAI titer ≥ 10 (1/dil)
    Percentage of participants with HAI titer ≥ 10 (1/dil)
  6. GMTs of Abs against investigational pandemic flu H5 HA mRNA SD2 vaccine
    Ab titer measured by seroneutralization (SN) test
  7. Individual SN titer ratio
    GMR SN titers ratio
  8. SN titer ≥ 20 (1/dil)
    Percentage of participants with SN titer ≥ 20 (1/dil)
  9. SN titer ≥ 40 (1/dil)
    Percentage of participants with SN titer ≥ 40 (1/dil)
  10. SN titer ≥ 80 (1/dil)
    Percentage of participants with SN titer ≥ 80 (1/dil)
  11. Detectable SN titer ≥ 10 (1/dil)
    Percentage of participants with SN titer ≥ 10 (1/dil)
  12. 2-fold and 4-fold rise in SN titer
    Percentage of participants with fold increase in SN Ab titer \[post-vaccination / pre- vaccination\] ≥ 2 and ≥ 4 on D22 and D43

Eligibility Criteria

Ages Eligible for Study(Adult, Older Adult)
Sexes Eligible for StudyAll
Accepts Healthy VolunteersYes
Inclusion Criteria
Aged 18 years or older on the day of inclusion
A female participant is eligible to participate if she is not pregnant or breastfeeding and one of the following conditions applies:
Is of non-childbearing potential. To be considered of non-childbearing potential, a female must be postmenopausal for at least 1 year, or surgically sterile. OR • Is of childbearing potential and agrees to use an effective contraceptive method or abstinence from at least 4 weeks prior to each study intervention administration until at least 12 weeks after the last study intervention administration
A female participant of childbearing potential must have a negative highly sensitive pregnancy test (urine or serum as required by local regulation) within 8 hours before the first dose of study intervention
Exclusion Criteria
Known or suspected congenital or acquired immunodeficiency; or receipt of immunosuppressive therapy, such as anti-cancer chemotherapy or radiation therapy, within the preceding 6 months; or long-term systemic corticosteroid therapy (prednisone or equivalent for more than 2 consecutive weeks within the past 3 months)
Known systemic hypersensitivity to any of the study intervention components (eg, polyethylene glycol, polysorbate); history of a life-threatening reaction to the study interventions used in the study or to a product containing any of the same substances; any allergic reaction (eg, anaphylaxis) after administration of an mRNA vaccine
Previous history of myocarditis, pericarditis, and/or myopericarditis
Known history of previous episodes of Guillain-Barré Syndrome (GBS), neuritis (including Bell's palsy), convulsions , encephalitis, transverse myelitis, and vasculitis
Participants with an electrocardiogram that is consistent with possible myocarditis or pericarditis or, in the opinion of the investigator, demonstrates clinically relevant abnormalities that may affect participant safety or study results
Self-reported thrombocytopenia, contraindicating IM injection based on investigator's judgment
Bleeding disorder, or receipt of anticoagulants in the 3 weeks preceding inclusion, contraindicating IM injection based on investigator's judgment
Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with study conduct or completion
Moderate or severe acute illness / infection (according to investigator's judgment) or febrile illness (temperature ≥ 38.0°C \[≥ 100.4°F\]) on the day of study intervention. A prospective participant should not be included in the study until the condition has resolved or the febrile event has subsided
Alcohol, prescription drug, or substance abuse that, in the opinion of the investigator, might interfere with the study conduct or completion
Participant who had acute infectious symptoms or a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse transcriptase polymerase chain reaction (RT PCR) or antigen test in the past 10 days prior to the first visit (V)01
Receipt of any vaccine other than an mRNA vaccine in the 4 weeks preceding study intervention administration or planned receipt of any vaccine other than an mRNA vaccine in the 3 weeks following the second dose of the study intervention
Receipt of immune globulins, blood or blood-derived products in the past 3 months
Receipt of any mRNA vaccine/product in the 2 months preceding study intervention administration or planned receipt of any mRNA vaccine in the 2 months after the second dose of the study intervention
Participation at the time of study enrollment (or in the 4 weeks preceding study intervention administration) or planned participation during the present study period in another clinical study investigating a vaccine, drug, medical device, or medical procedure
Previous history of participation in an H5 influenza A vaccine study. This includes any influenza subtypes that contain H5 such as H5N1, H5N8, or H5N6 Note: The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.

Contacts and Locations

Sponsors and CollaboratorsSanofi
Locations
Velocity Clinical Research - San Diego- Site Number : 8400013 | La Mesa California, United States, 91942Accel Research Sites Network - DeLand Clinical Research Unit- Site Number : 8400002 | DeLand Florida, United States, 32720Accel Research Sites - Lakeland Clinical Research Unit- Site Number : 8400006 | Lakeland Florida, United States, 33803Accel Research Sites - St. Petersburg - Largo- Site Number : 8400004 | Largo Florida, United States, 33777Accel Research Site - NeuroStudies.net, LLC - ERN - PPDS- Site Number : 8400003 | Decatur Georgia, United States, 30030-2627QUEST Research Institute- Site Number : 8400014 | Bingham Farms Michigan, United States, 48334Velocity Clinical Research - Norfolk- Site Number : 8400015 | Norfolk Nebraska, United States, 68701Velocity Clinical Research - Omaha- Site Number : 8400012 | Omaha Nebraska, United States, 68134Velocity Clinical Research - Springdale- Site Number : 8400010 | Cincinnati Ohio, United States, 45246Coastal Carolina Research Center- Site Number : 8400001 | North Charleston South Carolina, United States, 29406Olympus Clinical Research - Sugar Land- Site Number : 8400009 | Sugar Land Texas, United States, 77479Velocity Clinical Research - Salt Lake City- Site Number : 8400011 | West Jordan Utah, United States, 84088Charlottesville Medical Research- Site Number : 8400005 | Charlottesville Virginia, United States, 22911