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NCT Number: NCT07516418

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 purpose of this study is to evaluate the safety and immunogenicity of different formulations of vaccines encoding the RSV monovalent antigen or the Flu hemagglutinin subtype 5 (H5) antigen in healthy participants aged 18 to 49 years.

The total duration of study participation for each participant varies by stage and treatment arm.

Stage 1:

* For Arm 1, Arm 2, and Arm 3 the duration of study participation will be approximately 7 months for each participant. * For Arm 4, Arm 5, and Arm 6 the duration of study participation will be approximately 6 months for each participant.

Stage 2: For all arms, the duration of study participation will be approximately 7 months for each participant.

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Key information

Conditions

Respiratory Syncytial Virus (RSV) Infections Influenza A(H5N1) Influenza, Human Mononegavirales Infections Orthomyxoviridae Infections Paramyxoviridae Infections Pneumovirus Infections RNA Virus Infections Respiratory Syncytial Virus Infections Respiratory Tract Diseases Respiratory Tract Infections Virus Diseases

Age range

18 year–49 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 1

Primary location

Site # 0361002, Griffith, Queensland, Australia

Loading trial locations.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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 for at least 1 year, or surgically sterile. OR
  • Is of CBP (Child-Bearing Potential) and uses an effective contraceptive method or abstinence from at least 4 weeks prior to study intervention administration until at least 12 weeks after the last study intervention administration.

Exclusion criteria

  • Any condition which, in the opinion of the Investigator, might interfere with the evaluation of the study objectives

The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.

Treatment and study plan

H5 Flu Investigational Medical Product (IMP) 1

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

H5 Flu IMP 2

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

H5 Flu IMP 3

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

RSV IMP 4

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

RSV IMP 5

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

RSV IMP 6

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

H5 Flu IMP 7

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

H5 Flu IMP 8

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

H5 Flu IMP 9

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

H5 Flu IMP 10

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

H5 Flu IMP 11

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

H5 Flu IMP 12

Biological

Suspension for injection. Route of administration: Intramuscular (IM) injection

Primary outcomes

  1. Presence of any unsolicited systemic Adverse Events (AEs) reported within 30 minutes after vaccination

    Time frame: On Day 1

  2. 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

    Time frame: Day 1 through day 8

  3. 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

    Time frame: Day 1 through day 8

  4. Presence of unsolicited AEs reported through 20 days after the first vaccination and after the second vaccination for IMPs with the Flu H5 antigen

    Time frame: Day 1 through day 21

  5. Presence of unsolicited AEs reported through 28 days after vaccination for IMPs with the RSV antigen

    Time frame: Day 1 through day 29

  6. Presence of SAEs (Serious Adverse Events) and AESIs (Adverse Events of Special Interest) throughout the study (ie, through 6 months after vaccination)

    Time frame: 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)

  7. Presence of out-of-range biological test results (including shift from baseline values) through 7 days after each vaccination

    Time frame: Screening through day 8

  8. Presence of AEs leading to study discontinuation throughout the study (ie, through 6 months after vaccination)

    Time frame: Screening through day 202 (IMPs containing Flu H5 antigen), Screening through day 181 (IMPs containing RSV antigen)

  9. 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

    Time frame: Day 1 and day 29

  10. 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

    Time frame: Day 1, day 22 and day 43

  11. 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

    Time frame: 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.

  12. 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

    Time frame: Day 1, day 22 and day 43

  13. 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

    Time frame: Day 1, day 22, and day 43

  14. 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

    Time frame: Day 1, day 22, and day 43

Secondary outcomes

  1. 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

    Time frame: Day 1, day 22, and day 43

  2. Neutralizing antibody titer ratio at pre-vaccination and 21 and 42 days post-vaccination in all participants receiving IMPs with the Flu H5 antigen

    Time frame: Day 1, day 22, and day 43

    Ratio of post-vaccination to pre-vaccination neutralizing antibody titers, calculated as Day 22/Day 1 and Day 43/Day 1 using a validated neutralization (NT) assay.

  3. 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

    Time frame: Day 1, day 22, and day 43

  4. Proportion of participants with detectable neutralizing antibody titers ≥10 at pre-vaccination and 21 and 42 days post-vaccination in all participants receiving IMPs with the Flu H5 antigen

    Time frame: Day 1, day 22, and day 43

  5. Proportion of participants with ≥2-fold and ≥4-fold increase in neutralizing antibody titers at pre-vaccination and 21 and 42 days post-vaccination in all participants receiving IMPs with the Flu H5 antigen

    Time frame: Day 1, day 22, and day 43

Study contacts

Contact information is provided by the study sponsor or research team.

Sanofi Trial Transparency Email Recommended (Toll free for US and Canada)

CONTACT

[email protected]

800-633-1610 ext. Opt. 6

Sponsors and collaborators

Lead sponsor

Sanofi

Industry

Registry information

Official study title

A Phase 1, Randomized, Multi-center Study to Evaluate the Safety and Immunogenicity of Different Formulations of Vaccines Encoding the RSV Monovalent Antigen or the Flu H5 Antigen in Healthy Participants 18 to 49 Years of Age

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
Apr 8, 2026
Registry last updated
May 8, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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