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Yellow FeverPhase 2NCT05011123

Study on an Investigational Yellow Fever Vaccine Compared With Stamaril in Adults in Europe and Asia

A Phase 2 study testing Yellow fever vaccine (produced on serum-free Vero cells) and Yellow fever vaccine in people with Yellow Fever, run by Sanofi Pasteur, a Sanofi Company at 23 sites in 6 countries.

Active, not recruiting

Under way, not looking for participants. Everyone needed has enrolled. The study is still running.

Official record
Search all trials

Trial summary

VYF03 is a phase II, randomized, parallel-group prevention study with 2 arms, active-controlled (Stamaril), observer-blind, multi-center study to assess the non-inferiority of the immune response, in terms of seroconversion rates of the investigational vaccine candidate vYF to the licensed Stamaril, in adults aged 18… Read more about this study

Who is it for?
Ages 18 to 59 yearsHealthy volunteers can take part
Conditions the study is for
Yellow Fever
What is being tested?
Yellow fever vaccine (produced on serum-free Vero cells) and Yellow fever vaccine
Could I receive a placebo?
No, everyone receives an active treatment
How many people
690 participants
Where
23 sitesin 6 countries
Study dates
7 Oct 2021to 23 Apr 2027
Phase
Phase 2
Are there results?
Yes, posted in the registrySummary in the doctors' view

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 to 59 years
  • All sexes
  • Healthy volunteers accepted
  • Adult

Who may be able to join

  • Aged 18 years up to 60 years* 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 (1) or abstinence (1) from at least 4 weeks prior to study intervention administration until at least 4 weeks (2) after study intervention administration.
  • 18 to 60 years means from the day of the 18th birthday up to the day before the 60th birthday
  • Not applicable for Finland
  • Except for French participants which have to apply 12 weeks contraception after 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) before any dose of study intervention on Day 1 and the test will be repeated on D29 to confirm the participant is still not pregnant within 28 days of vaccine administration.
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  • Informed consent form has been signed and dated (3)
  • For participants aged less than 21 years in Singapore, an informed consent form has been signed and dated by both the participant and the parent(s) or another legally acceptable representative
  • Able to attend all scheduled visits and to comply with all study procedures
  • For participants enrolled in Asian countries as part of the additional cohort only: know Chinese origin, defined as having at least one biological parent of Chinese origin, and will be self-reported by the participant

Who cannot join

  • Participation at the time of study enrollment (or in the 4 weeks preceding the study vaccination) or planned participation during the first 2 years of the 5-year follow-up in another clinical study investigating a vaccine, drug, medical device, or medical procedure. Enrollment in another study after the first 2 years is permitted, assuming that it does not exclude participation in this study.
  • Receipt of any vaccine in the 4 weeks preceding the study vaccination or planned receipt of any vaccine in the 4 weeks following the study vaccination (prior to visit 4), except for influenza vaccination, which may be received at least 2 weeks before study vaccines (4). This exception includes all influenza vaccines including monovalent pandemic influenza vaccines.
  • Previous vaccination against a FV disease at any time including YF with either the study vaccine or another vaccine.
  • Receipt of immune globulins, blood, or blood-derived products in the past 6 months.
  • 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 history of any FV infection.
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  • Known systemic hypersensitivity to any of the vaccine components, eggs, or history of a life-threatening reaction to the vaccines used in the study or to a vaccine containing any of the same substances.
  • Known history or laboratory evidence of HIV infection (5).
  • Known history or laboratory evidence of hepatitis B or hepatitis C infection (6).
  • Personal or family history of thymic pathology (thymoma, thymectomy, or myasthenia).
  • Deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized involuntarily.
  • Alcohol, prescription drug, or substance abuse that, in the opinion of the Investigator, might interfere with the study conduct or completion.
  • Chronic illness (7) that, in the opinion of the Investigator, is at a stage where it might interfere with trial conduct or completion, including malignancy, such as leukemia, or lymphoma.
  • Moderate or severe acute illness/infection (according to Investigator judgment) on the day of vaccination or febrile illness (temperature ≥ 100.4°F or 38°C). A prospective participant should not be included in the study until the condition has resolved or the febrile event has subsided.
  • Administration of any anti-viral within 2 months preceding the vaccination and planned administration up to the 6 weeks following the vaccination.
  • Identified as an Investigator or employee of the Investigator or study center with direct involvement in the proposed study, or identified as an immediate family member (ie, parent, spouse, natural or adopted child) of the Investigator or employee with direct involvement in the proposed study.
  • Planned travel in a YF endemic country within 6 months of investigational or control vaccine administration.
  • Except for Thai participants
  • HIV Serology testing will be performed on all German participants if no evidence of seronegativity in the 90 days preceding vaccination
  • Hepatitis B and Hepatitis C Serology testing will be performed on all German participants if no evidence of seronegativity in the 90 days preceding vaccination
  • Chronic illness may include, but is not limited to, cardiac disorders, renal disorders, auto-immune disorders, diabetes, psychiatric disorders or chronic infection

Trial locations and contacts

23 sites in 6 countries.

23 sites in 6 countries

France6 sites

  • Investigational Site Number : 2500008

    Lyon, 69004

  • Investigational Site Number : 2500006

    Montpellier, 34295

  • Investigational Site Number : 2500001

    Nantes, 44093

  • Investigational Site Number : 2500007

    Nîmes, 30029

  • Investigational Site Number : 2500009

    Paris, 75014

  • Investigational Site Number : 2500004

    Pierre-Bénite, 69495

Other trials in France

Germany4 sites

  • Investigational Site Number : 2760004

    Berlin, 10117

  • Investigational Site Number : 2760001

    Hamburg, 20359

  • Investigational Site Number : 2760002

    München, 80802

  • Investigational Site Number : 2760003

    Rostock, 18057

Other trials in Germany

Spain4 sites

  • Investigational Site Number : 7240004

    Barcelona, Barcelona [Barcelona], 08035

  • Investigational Site Number : 7240001

    Barcelona, 08036

  • Investigational Site Number : 7240003

    L'Hospitalet de Llobregat, Barcelona [Barcelona], 08907

  • Investigational Site Number : 7240002

    Madrid, Madrid, Comunidad de, 28046

Other trials in Spain

Finland3 sites

  • Investigational Site Number : 2460001

    Helsinki, 00290

  • Investigational Site Number : 2460002

    Tampere, 33100

  • Investigational Site Number : 2460003

    Turku, 20520

Other trials in Finland

Singapore3 sites

  • Investigational Site Number : 7020002

    Singapore, 119074

  • Investigational Site Number : 7020003

    Singapore, 169608

  • Investigational Site Number : 7020001

    Singapore

Other trials in Singapore

Thailand3 sites

  • Investigational Site Number : 7640001

    Bangkok, 10330

  • Investigational Site Number : 7640002

    Bangkok

  • Investigational Site Number : 7640003

    Nonthaburi, 11000

Other trials in Thailand

About this study

Official title: Controlled Study of Immunogenicity and Safety of the Investigational vYF Candidate Vaccine in Comparison to Stamaril in Adults

VYF03 is a phase II, randomized, parallel-group prevention study with 2 arms, active-controlled (Stamaril), observer-blind, multi-center study to assess the non-inferiority of the immune response, in terms of seroconversion rates of the investigational vaccine candidate vYF to the licensed Stamaril, in adults aged 18 years up to 60 years in Europe (EU).

The safety and immunogenicity profile of vYF in a cohort of Asian population of Chinese origin outside of China will also be described. The study will also assess the immunogenicity profiles and the safety profiles of vYF and Stamaril.

Read more

Participants will be randomized in a 2:1 ratio to receive a single subcutaneous injection of either the vYF vaccine (380 participants in EU and 80 participants of Chinese origin in Asia) or Stamaril (190 participants in EU and 40 participants of Chinese origin in Asia), on Day 01.

The duration of each participant's participation will be approximately 5 years.

Read the detailed description

The duration of each participant's participation will be approximately 5 years.

Conditions
Yellow Fever
Being tested
Yellow fever vaccine (produced on serum-free Vero cells), Yellow fever vaccine
Medical subject headings
Yellow Fever

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • Yellow fever vaccine (produced on serum-free Vero cells)Biological

    Also called vYF vaccine

    Powder and diluent for suspension for injection - Subcutaneous

  • Yellow fever vaccineBiological

    Also called Stamaril

    Powder and diluent for suspension for injection - Subcutaneous

Study groups in NCT05011123
Study groupRoleWhat they receive
Group 1Experimental1 injection of vYF vaccine at Day 1
Receives: Biological: Yellow fever vaccine (produced on serum-free Vero cells)
Group 2Active comparator1 injection of Stamaril vaccine at Day 1
Receives: Biological: Yellow fever vaccine

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Percentage of Yellow Fever-naive Participants Who Achieved Seroconversion 28 Days Post Dose 1 Enrolled in European Union

    Seroconversion was defined as a 4-fold increase in Nab titers as compared to the pre-vaccination value. YF-naive participants (or negative) at baseline corresponded to participants with no detectable YF Ab titers before vaccination. The YF NAb titers were determined using a validated live virus microneutralization (MN) assay. Percentages are rounded off to the tenth decimal place.

    Measured: 28 days post dose 1 (Day 29)

Secondary outcomes (12)

  1. Percentage of Participants Who Achieved Seroconversion 28 Days Post Dose 1 Enrolled in European Union

    Seroconversion was defined as a 4-fold increase in Nab titers as compared to the pre-vaccination value. The YF NAb titers were determined using a validated live virus MN assay. Percentages are rounded off to the tenth decimal place.

    Measured: 28 days post dose 1 (Day 29)

  2. Percentage of Participants Who Achieved Seroconversion Enrolled in European Union and Asia

    Seroconversion was defined as a 4-fold increase in Nab titers as compared to the pre-vaccination value: as compared to the Day 1 titers at each timepoint up to Month 6; as compared to the last planned previous timepoint from Year 1 onwards. The YF NAb titers were determined using a validated live virus MN assay. Percentages are rounded off to the tenth decimal place.

    Measured: Days 1, 11, 29, Month 6, Years 1 and 2

  3. Percentage of Participants Who Achieved Seroprotection to Yellow Fever Virus Enrolled in European Union and Asia

    Seroprotection was defined as NAb titers >=threshold of 10 (1/dilution). YF-naive participants (or negative) at baseline corresponded to participants with no detectable YF Ab titers before vaccination. The YF NAb titers were determined using a validated live virus MN assay. Percentages are rounded off to the tenth decimal place.

    Measured: Days 1, 11, 29, Month 6, Years 1 and 2

  4. Geometric Mean Titers (GMTs) of Antibodies Against Yellow Fever Virus in Participants Enrolled in European Union and Asia

    GMTs of antibody against YF virus was measured using a validated live virus MN assay.

    Measured: Days 1, 11, 29, Month 6, Years 1 and 2

  5. Geometric Mean Titers Ratio (GMTRs) of Antibodies Against Yellow Fever Virus in Participants Enrolled in European Union and Asia

    GMTs of antibody against YF virus was measured using a validated live virus MN assay. Ratio was calculated as post-vaccination titer at Days 11, 29 and Month 6 to pre-vaccination titer at Day 1; post-vaccination titer at Year 1 to pre-vaccination titer at Month 6; post-vaccination titer at Year 2 to pre-vaccination titer at Year 1.

    Measured: Days 1, 11, 29, Month 6, Years 1 and 2

  6. Number of Participants With Unsolicited Systemic Adverse Events (AEs)

    An unsolicited AE was an observed AE that did not fulfill the conditions of solicited reactions, ie, pre-listed in the CRF in terms of diagnosis and onset window post-vaccination.

    Measured: Up to 30 minutes post vaccination on Day 1

  7. Number of Participants With Solicited Injection Site Reactions

    A solicited reaction was an "expected" adverse reaction (AR) (sign or symptom) observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRF. An injection site reaction was an AR at and around the injection site of the study vaccine.

    Measured: Up to 7 days post vaccination (Day 8)

  8. Number of Participants With Solicited Systemic Reactions

    A solicited reaction was an "expected" AR (sign or symptom) observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRF. Solicited systemic reactions were systemic AEs observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRF.

    Measured: Up to 14 days post vaccination (Day 15)

  9. Number of Participants With Unsolicited Adverse Events

    An unsolicited AE was an observed AE that did not fulfill the conditions of solicited reactions, ie, pre-listed in the CRF in terms of diagnosis and onset window post-vaccination.

    Measured: Up to 28 days post vaccination (Day 29)

  10. Number of Participants With Any Serious Adverse Events (SAEs) and Adverse Events of Special Interest (AESIs) up to 6 Months Post-Vaccination

    An SAE was any AE that at any dose resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, was a congenital anomaly/birth defect, or was an important medical event. An AESI (serious or non-serious) was defined as one of scientific and medical concern specific to the Sponsor's study intervention or program, for which ongoing monitoring and rapid communication by the Investigator to the Sponsor could be appropriate. AESIs included serious hypersensitivity/allergic reactions, organ failure/serious viscerotropic events, serious neurologic events.

    Measured: From the first dose of study vaccine administration (Day 1) up to 6 months post vaccination, approximately up to Day 181

  11. Number of Participants With Serious Adverse Events and Deaths up to Day 1030

    An SAE was any AE that at any dose resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, was a congenital anomaly/birth defect, or was an important medical event.

    Measured: From the first dose of study vaccine administration (Day 1) up to DBL date of 01 August 2024, approximately up to Day 1030

  12. Number of Participants With Serious Adverse Events and Deaths Up to Year 5

    An SAE was any AE that at any dose resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, was a congenital anomaly/birth defect, or was an important medical event.

    Measured: From the first dose of study vaccine administration (Day 1) up to end of study, approximately 5 years

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted18 Aug 2021
  2. Study start7 Oct 2021
  3. Primary completion23 May 2022
  4. Study completion23 Apr 2027 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 2
Primary purpose
Prevention
Allocation
Randomised
Intervention model
Parallel groups
Masking
Quadruple blind
Who is masked
Participant, Care provider, Investigator, Outcomes assessor
Enrolment
690 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT05011123
Sponsor's protocol ID
VYF03
Other IDs
U1111-1260-4650, 2022-502047-35, 2020-005566-33
Status last verified
May 2026
First submitted
17 Aug 2021
Last updated
1 Jun 2026
Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
Yes: Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing Yellow fever vaccine (produced on serum-free Vero cells) and Yellow fever vaccine in people with Yellow Fever, run by Sanofi Pasteur, a Sanofi Company at 23 sites in 6 countries.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 10 inclusion and 21 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: under way, not looking for participants, as of the sponsor's last update on 1 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 23 sites in France, Germany, Spain, Finland, Singapore and 1 more country. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

Yes. Results are posted in the registry (first posted 21 May 2025). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Percentage of Yellow Fever-naive Participants Who Achieved Seroconversion 28 Days Post Dose 1 Enrolled in European Union (time frame: 28 days post dose 1 (Day 29)). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05011123.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 1 Jun 2026.

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