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H5 influenza mRNA vaccine candidate

Phase 1

Respiratory Syncytial Virus (RSV) | Vaccine | Infectious Disease |Sanofi|Trials Updated: May 8, 2026

H5 influenza mRNA vaccine candidate target and mechanism

ModalityVaccine

Also known as H5 Flu Investigational Medical Product (IMP) 1, H5 Flu Investigational Medical Product 1, H5 Flu IMP 2

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindCONTROLLED
Total Trials1
Total Enrollment570

FDA Designations

No designations recorded

H5 influenza mRNA vaccine candidate clinical trials

H5 influenza mRNA vaccine candidate · 1 trial · 2 indications

Phase 1 1
NCT07516418Study of Different Formulations of Vaccines Encoding the RSV Monovalent Antigen or the Flu H5 Antigen in Participants 18 to 49 Years of AgeRespiratory Syncytial Virus (RSV)
RECRUITING570 Analytics
PHASE1RECRUITING
Study of Different Formulations of Vaccines Encoding the RSV Monovalent Antigen or the Flu H5 Antigen in Participants 18 to 49 Years of Age
Respiratory Syncytial Virus (RSV)
NCT07516418570
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Study Endpoints

Primary Endpoints

Presence of any unsolicited systemic Adverse Events (AEs) reported within 30 minutes after vaccination
On Day 1
Presence of solicited injection site reactions (ie, injection site pain, injection site erythema, injection site swelling, pre-listed in participant's diary and in the eCRF (electronic case report form)) occurring through 7 days after each vaccination
Day 1 through day 8
Presence of solicited systemic reactions (ie, fever, headache, and only new or worsened fatigue, myalgia, arthralgia, and chills pre-listed in the participant's diary and in the eCRF) occurring through 7 days after each vaccination
Day 1 through day 8
Presence of unsolicited AEs reported through 20 days after the first vaccination and after the second vaccination for IMPs with the Flu H5 antigen
Day 1 through day 21
Presence of unsolicited AEs reported through 28 days after vaccination for IMPs with the RSV antigen
Day 1 through day 29
Presence of SAEs (Serious Adverse Events) and AESIs (Adverse Events of Special Interest) throughout the study (ie, through 6 months after vaccination)
SAE: Screening day through day 202 (IMPs containing Flu H5 antigen), Screening day through day 181 (IMPs containing RSV antigen); AESI: Day 1 through day 202 (IMPs containing Flu H5 antigen), Day 1 through day 181 (IMPs containing RSV antigen)
Presence of out-of-range biological test results (including shift from baseline values) through 7 days after each vaccination
Screening through day 8
Presence of AEs leading to study discontinuation throughout the study (ie, through 6 months after vaccination)
Screening through day 202 (IMPs containing Flu H5 antigen), Screening through day 181 (IMPs containing RSV antigen)
RSV A and RSV B serum nAb (neutralizing antibodies) titers at pre-vaccination and 28 days post-vaccination in all participants receiving IMPs with the RSV antigen
Day 1 and day 29
Flu H5 antibody (Ab) titer measured by hemagglutination inhibition (HAI) at pre-vaccination and 21 and 42 days post-vaccination in all participants receiving IMPs with the Flu H5 antigen
Day 1, day 22 and day 43
Hemagglutination Inhibition (HAI) geometric mean titer ratio at 21 and 42 days post-vaccination relative to pre-vaccination for all participants receiving IMPs with the Flu H5 antigen
Day 1, day 22 and day 43

Ratio of post-vaccination to pre-vaccination hemagglutination inhibition (HAI) antibody titers, calculated as Day 22/Day 1 and Day 43/Day 1.

Seroconversion rate based on Hemagglutination inhibition (HAI) antibody titers at pre-vaccination and 21 and 42 days post-vaccination in all participants receiving IMPs with the Flu H5 antigen
Day 1, day 22 and day 43
Proportion of participants with Hemagglutination Inhibition (HAI) antibody titer ≥40 at pre-vaccination and 21 and 42 days post-vaccination in all participants receiving IMPs with the Flu H5 antigen
Day 1, day 22, and day 43
Proportion of participants with detectable HAI antibody titer ≥10 at pre-vaccination and 21 and 42 days post-vaccination in all participants receiving IMPs with the Flu H5 antigen
Day 1, day 22, and day 43

Secondary Endpoints

Geometric mean neutralizing antibody titers measured by Neutralization Assay (NT) at pre-vaccination and 21 and 42 days post-vaccination in all participants receiving IMPs with the Flu H5 antigen
Day 1, day 22, and day 43
Neutralizing antibody titer ratio at pre-vaccination and 21 and 42 days post-vaccination in all participants receiving IMPs with the Flu H5 antigen
Day 1, day 22, and day 43
Proportion of participants with neutralizing antibody titers ≥20, ≥40, and ≥80 at pre-vaccination and 21 and 42 days post-vaccination in all participants receiving IMPs with the Flu H5 antigen
Day 1, day 22, and day 43
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Study Design & Arms

AllocationRANDOMIZED
MaskingTRIPLE
ModelSEQUENTIAL
PurposePREVENTION

Treatment Arms

ArmTypeDescription
Stage 1, Arm 1EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 and day 22 of the H5 Flu vaccines according to their randomization schedule.
Stage 1, Arm 2EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 and day 22 of the H5 Flu vaccines according to their randomization schedule.
Stage 1, Arm 3EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 and day 22 of the H5 Flu vaccines according to their randomization schedule.
Stage 1, Arm 4EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 of the RSV vaccines according to their randomization schedule.
Stage 1, Arm 5EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 of the RSV vaccines according to their randomization schedule.
Stage 1, Arm 6EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 of the RSV vaccines according to their randomization schedule.
Stage 2, Arm 1EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 and day 22 of the H5 Flu vaccines according to their randomization schedule.
Stage 2, Arm 2EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 and day 22 of the H5 Flu vaccines according to their randomization schedule.
Stage 2, Arm 3EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 and day 22 of the H5 Flu vaccines according to their randomization schedule.
Stage 2, Arm 4EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 and day 22 of the H5 Flu vaccines according to their randomization schedule.
Stage 2, Arm 5EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 and day 22 of the H5 Flu vaccines according to their randomization schedule.
Stage 2, Arm 6EXPERIMENTALParticipants will receive a single IM (Intramuscular) injection on day 1 and day 22 of the H5 Flu vaccines according to their randomization schedule.

Interventions

NameTypeDescription
H5 Flu Investigational Medical Product (IMP) 1BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
H5 Flu IMP 2BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
H5 Flu IMP 3BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
RSV IMP 4BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
RSV IMP 5BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
RSV IMP 6BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
H5 Flu IMP 7BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
H5 Flu IMP 8BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
H5 Flu IMP 9BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
H5 Flu IMP 10BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
H5 Flu IMP 11BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
H5 Flu IMP 12BIOLOGICALSuspension for injection. Route of administration: Intramuscular (IM) injection
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Eligibility Criteria

Age Range18 Years to 49 Years
SexALL
Healthy VolunteersYes
Study Sites6

Inclusion Criteria: * Aged 18 to 49 years on the day of inclusion * A female participant is eligible to participate if she is not pregnant or breastfeeding and of the following conditions applies: * Is of NCBP (Non-Child-Bearing Potential). To be considered of NCBP, a female must be post-menopausal...

Countries:Australia
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Frequently asked questions about H5 influenza mRNA vaccine candidate

What is the H5 influenza mRNA vaccine candidate?

The H5 influenza mRNA vaccine candidate is an investigational mRNA vaccine developed by Sanofi that encodes the influenza A(H5) antigen. It is being studied in healthy adult volunteers as part of a Phase 1 trial that also evaluates formulations encoding an RSV monovalent antigen. It is not approved and remains in clinical development.

What is the H5 influenza mRNA vaccine candidate used for?

The H5 influenza mRNA vaccine candidate is being studied for protection against influenza A(H5N1). The Phase 1 trial enrolling participants 18 to 49 years of age lists Influenza A(H5N1) and Respiratory Syncytial Virus (RSV) among its conditions, with the H5 antigen evaluated alongside RSV-encoding formulations.

Who is developing the H5 influenza mRNA vaccine candidate?

Sanofi is developing the H5 influenza mRNA vaccine candidate. Sanofi trades on the New York Stock Exchange under the ticker SNY. The company is running the candidate through a Phase 1 study conducted in Australia.

What phase is the H5 influenza mRNA vaccine candidate in?

The H5 influenza mRNA vaccine candidate is in Phase 1. It is an investigational product and has not been approved by the FDA. One Phase 1 trial is currently recruiting, with no completed trials reported for this candidate.

What clinical trials is the H5 influenza mRNA vaccine candidate in?

The H5 influenza mRNA vaccine candidate is being evaluated in NCT07516418, titled Study of Different Formulations of Vaccines Encoding the RSV Monovalent Antigen or the Flu H5 Antigen in Participants 18 to 49 Years of Age. The trial is a recruiting Phase 1 study with 570 participants in Australia.

Is the H5 influenza mRNA vaccine candidate the same as H5 Flu Investigational Medical Product (IMP) 1?

Yes. The H5 influenza mRNA vaccine candidate is also referred to as H5 Flu Investigational Medical Product (IMP) 1, H5 Flu Investigational Medical Product 1, and H5 Flu IMP 2. These names refer to the same Sanofi Phase 1 mRNA vaccine program studied in NCT07516418.

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