Yellow Fever ImmunizationPhase 3NCT07103148
A Phase III Control Study of the Safety and Immunogenicity of vYF in Pediatric Population
A Phase 3 study testing Yellow fever vaccine (live) and Measles, combinations with mumps and rubella, live attenuated in people with Yellow Fever Immunization, run by Sanofi at 15 sites in 3 countries.
Trial summary
The purpose of this study is to determine whether vYF (investigational vaccine) is safe and can help the body to develop antibodies (immunogenicity) compared with Stamaril vaccine and YF-VAX vaccine (both licensed vaccines) and when they are co-administered with Measles Mumps Rubella (MMR) vaccines in infants aged… Read more about this study
- Who is it for?
- Ages 9 months to 5 yearsHealthy volunteers can take part
- Conditions the study is for
- Yellow Fever Immunization
- What is being tested?
- Yellow fever vaccine (live) and Measles, combinations with mumps and rubella, live attenuated
- Type of treatment
- Vaccines, Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 2,440 participants
- Where
- 15 sitesin 3 countries
- Study dates
- 11 Jul 2025to 4 Mar 2030
- Phase
- Phase 3
- Are there results?
- Not yet: the study is under way
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 9 months to 5 years
- All sexes
- Healthy volunteers accepted
- Child
Who may be able to join
- Aged 9 months to 5 years on the day of inclusion*
- "9 months to 5 years" means from the day of the 9th month after birth to the day before the 6th year birthday
- Aged 11 to 15 months* on the day of inclusion for participants enrolled in the MMR co-administration group
- "11 to 15 months" means from the day of the 11th month after birth to the day before the 16th month birthday
- Participants who are healthy as determined by medical evaluation including medical history and physical examination
- For infants*, born after a gestation period of 27 through 36 weeks and medically stable as assessed by the investigator, based on the following definition: "Medically stable" refers to the condition of premature infants who do not require significant medical support or ongoing management for debilitating disease and who have demonstrated a clinical course of sustained recovery by the time they receive the first dose of study intervention
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- Infants aged 9 months to 11 months up to the day before the 12th month birthday
- Participant and parent/LAR are able to attend all scheduled visits and to comply with all study procedures
- ICF has been signed and dated by the parent(s) or other LAR (and by an independent witness if required by local regulations)
Who cannot join
- Participants are excluded from the study if any of the following criteria apply:
- Known or suspected congenital or acquired immunodeficiency; or receipt of immunosuppressive therapy, such as anti-cancer chemotherapy irradiation 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 FV infection
- Known systemic hypersensitivity to any of the study intervention components, eggs or history of a life-threatening reaction to the study interventions used in the study or to a product containing any of the same substances
- Moderate or severe acute illness/infection (according to Investigator judgment) or febrile illness (temperature ≥ 38.0°C [≥ 100.4°F]) on the day of study intervention administration. A prospective participant should not be included in the study until the condition has resolved or the febrile event has subsided.
- Chronic illness* that, in the opinion of the Investigator, is at a stage where it might interfere with study conduct or completion , including malignancy, such as leukemia, or lymphoma
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- Chronic illness may include, but is not limited to, cardiac disorders, renal disorders, auto-immune disorders, diabetes, psychiatric disorders or chronic infection
- History of central nervous system disorder or disease, including seizures and febrile seizures
- Receipt of any vaccine in the 4 weeks preceding the study intervention administration or planned receipt of any vaccine in the 4 weeks following the study intervention administration. Vaccine to be administered as part of the National Immunization Schedule will be postponed after the D29 visit
- Previous vaccination against a FV disease at any time including YF with an investigational or marketed vaccine
- Receipt of immune globulins, blood or blood-derived products in the past 6 months
- Administration of any anti-viral within 2 months preceding the study intervention administration and up to the 6 weeks following the study intervention administration
- For participants enrolled in the MMR co-administration group: previous vaccination against measles, measles/mumps/rubella
- For participants enrolled in the MMR co-administration group: history of measles, mumps, rubella confirmed either clinically, serologically, or microbiologically
- Known history or laboratory evidence of HIV infection
- Known history of hepatitis B or hepatitis C seropositivity
- Personal or family history of thymic pathology (thymoma, thymectomy, or myasthenia)
- Participation at the time of study enrollment (or in the 4 weeks preceding the study intervention administration) or planned participation during the first year of the 3-year follow-up in another clinical study investigating a vaccine, drug, medical device, or medical procedure. Enrollment in another study after the first 6 months of follow-up is permitted, assuming it does not exclude participation in this study.
- In an emergency setting, or hospitalized involuntary
- Identified as a natural or adopted child of the Investigator or employee with direct involvement in the proposed study
Trial locations and contacts
15 sites in 3 countries. Contact the study team or a site near you to ask about taking part.
Trial Transparency email recommended (Toll free for US & Canada) contact
15 sites in 3 countries
Mexico7 sites, 7 recruiting
- Recruiting
Investigational Site Number : 4840011
Acapulco de Juárez, Guerrero, 39670
- Recruiting
Investigational Site Number : 4840009
Chihuahua City, 31000
- Recruiting
Investigational Site Number : 4840013
Cuernavaca, Morelos, 62290
- Recruiting
Investigational Site Number : 4840005
Ecatepec de Morelos, 55075
- Recruiting
Investigational Site Number : 4840001
Mexico City, 06760
- Recruiting
Investigational Site Number : 4840015
Tizimín, Yucatán, 97700
- Recruiting
Investigational Site Number : 4840007
Torreón, Coahuila, 27000
Honduras5 sites, 5 recruiting
- Recruiting
Investigational Site Number : 3400001
San Pedro Sula, 21104
- Recruiting
Investigational Site Number : 3400005
San Pedro Sula, 21104
- Recruiting
Investigational Site Number : 3400002
Tegucigalpa, 11101
- Recruiting
Investigational Site Number : 3400003
Tegucigalpa, 11101
- Recruiting
Investigational Site Number : 3400007
Tegucigalpa, 11101
Panama3 sites, 3 recruiting
- Recruiting
Investigational Site Number : 5910001
Panama City, 10662
- Recruiting
Investigational Site Number : 5910002
Panama City, 10662
- Recruiting
Investigational Site Number : 5910003
Panama City, 10662
About this study
Official title: A Parallel Group, Phase III Randomized, Modified Double-blind, Active Controlled Study to Investigate the Immunogenicity and Safety of vYF Compared to Licensed YF Vaccines in Pediatric Population Aged 9 Months to 5 Years of Age
The purpose of this study is to determine whether vYF (investigational vaccine) is safe and can help the body to develop antibodies (immunogenicity) compared with Stamaril vaccine and YF-VAX vaccine (both licensed vaccines) and when they are co-administered with Measles Mumps Rubella (MMR) vaccines in infants aged 11-15 months.
Number of Participants:
Read more
A total of 2440 participants is planned to be enrolled in VYF04 study.
Study Arms and Duration:
Eligible participants will be randomized in 2 independent groups (9-24 months, 2-5 years) to receive 1 dose of either vYF or Stamaril or YF-VAX in a 2:1:1 ratio within each age group. An additional group with participants of 11-15 months of age will also receive at the same vaccination visit vYF and a single dose of MMR vaccine.
For the 2nd step (YF booster vaccine administration in a subset), at the Year (Y) 3 visit, a subset of 120 participants of the 9-24 months of age group who did receive a YF vaccine on Day(D) 01 will be invited to join a booster dose assessment (booster dose administered after the Y3 visit blood sample has been taken). Participants aged 11 to 15 months at the time of the concomitant administration of vYF and MMR will not be eligible for receiving a booster dose.
The duration of each participation will be approximately 3 years for all participants (including participants co-administered on D01 with vYF and MMR), and 6 more months post-booster dose administration for the participants enrolled in the booster subset.
Read the detailed description
The duration of each participant's participation will be up to approximately 3 years (not including booster phase in a subset)
The Phase III VYF04 is the first study to be carried out with the investigational vYF in pediatric populations.
- Conditions
- Yellow Fever Immunization
- Being tested
- Yellow fever vaccine (live), Measles, combinations with mumps and rubella, live attenuated
- Keywords
- Yellow fever
- 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 (live)Biological
Also called vYF vaccine
Powder and diluent for suspension for injection Subcutaneous
Yellow fever vaccine (live)Biological
Also called Stamaril vaccine
Powder and diluent for suspension for injection Subcutaneous
Yellow fever vaccine (live)Biological
Also called YF-VAX vaccine
Powder and diluent for suspension for injection Subcutaneous
Measles, combinations with mumps and rubella, live attenuatedBiological
Also called MMR II vaccine
Powder, lyophilized, for suspension for reconstitution Subcutaneous or intermuscular
| Study group | Role | What they receive |
|---|---|---|
| Group 1 (9-24 months) | Experimental | Primary vaccination phase: 1 injection of vYF vaccine at Day 1 Booster phase: 1 injection of vYF vaccine at Year 3 (in a subset) Receives: Biological: Yellow fever vaccine (live) |
| Group 2 (9-24 months) | Active comparator | Primary vaccination phase: 1 injection of Stamaril vaccine at Day 1 Booster phase: 1 injection of Stamaril vaccine at Year 3 (in a subset) Receives: Biological: Yellow fever vaccine (live) |
| Group 3 (9-24 months) | Active comparator | Primary vaccination phase: 1 injection of YF-VAX vaccine at Day 1 Booster phase: 1 injection of YF-VAX vaccine at Year 3 (in a subset) Receives: Biological: Yellow fever vaccine (live) |
| Group 4 (2-5 years) | Experimental | Primary vaccination phase: 1 injection of vYF vaccine at Day 1 Receives: Biological: Yellow fever vaccine (live) |
| Group 5 (2-5 years) | Active comparator | Primary vaccination phase: 1 injection of Stamaril vaccine at Day 1 Receives: Biological: Yellow fever vaccine (live) |
| Group 6 (2-5 years) | Active comparator | Primary vaccination phase: 1 injection of YF-VAX vaccine at Day 1 Receives: Biological: Yellow fever vaccine (live) |
| Group 7 (approximately 11-15 months) | Experimental | Primary vaccination phase: 1 injection of MMR vaccine at Day 1 in a cohort of 11 to 15 months of age vaccinated with vYF Receives: Biological: Yellow fever vaccine (live); Biological: Measles, combinations with mumps and rubella, live attenuated |
What is being measured
The primary outcome is the main question the study is designed to answer.
Percentage of participants with seroconversion to YF virus after 1 dose of vYF compared to seroconversion after 1 dose of the Stamaril in YF-naive participants (9-24 months)
Seroconversion rates will be assessed using a YF MN assay Seroconversion is defined as a 4-fold increase in NAb titers as compared to the pre-vaccination value
Measured: At Day 29, 28 days post-vaccination (on Day 01) with vYF or Stamaril
Percentage of participants with seroconversion to YF virus after 1 dose of vYF compared to seroconversion after 1 dose of the YF-VAX in YF-naive participants (9-24 months)
Seroconversion rates will be assessed using a YF MN assay Seroconversion is defined as a 4-fold increase in NAb titers as compared to the pre-vaccination value
Measured: At Day 29, 28 days post-vaccination (on Day 01) with vYF or YF-VAX
Percentage of participants with seroconversion to YF virus after 1 dose of vYF compared to seroconversion after 1 dose of the Stamaril in YF-naive participants (2-5 years)
Seroconversion rates will be assessed using a YF MN assay Seroconversion is defined as a 4-fold increase in NAb titers as compared to the pre-vaccination value
Measured: At Day 29, 28 days post-vaccination (on Day 01) with vYF or Stamaril
Percentage of participants with seroconversion to YF virus after 1 dose of vYF compared to seroconversion after 1 dose of the YF-VAX in YF-naive participants (2-5 years)
Seroconversion rates will be assessed using a YF MN assay Seroconversion is defined as a 4-fold increase in NAb titers as compared to the pre-vaccination value
Measured: At Day 29, 28 days post-vaccination (on Day 01) with vYF or YF-VAX
Secondary outcomes (29)
Percentage of participants, by age group, with seroconversion to YF virus in all investigational vaccine groups before (Day 01) and after investigational vaccine administration at various timepoints
Seroconversion rates will be assessed using a YF MN assay Seroconversion is defined as a 4-fold increase in NAb titers as compared to the pre-vaccination value
Measured: At Day 01 and at Day 11 (in a subset), Day 15 (in a subset), Day 29, Month 6, and yearly from Year 1 to Year 3
Percentage of participants, by age group, with seroprotection to YF virus in all investigational vaccine groups before (Day 01) and after investigational vaccine administration at various timepoints
Seroprotection is defined as NAb titers ≥ 10 (1/dil) at the corresponding timepoint
Measured: At Day 01 and at Day 11 (in a subset), Day 15 (in a subset), Day 29, Month 6, and yearly from Year 1 to Year 3
Geometric Mean Titers (GMTs) of neutralizing antibodies against YF virus in all investigational vaccine groups, by age group, before (Day 01) and after investigational vaccine administration at various timepoints
Antibody titers are expressed as geometric mean titers
Measured: At Day 01 and at Day 11 (in a subset), Day 15 (in a subset), Day 29, Month 6, and yearly from Year 1 to Year 3
Geometric Mean Titers Ratio (GMTRs) of neutralizing antibodies against YF virus in all investigational vaccine groups, by age group, before (Day 01) and after investigational vaccine administration at various timepoints
At Day 01 and at Day 11 (in a subset), Day 15 (in a subset), Day 29, Month 6, and yearly from Year 1 to Year 3
Measured: GMTRs Day 11/Day 01 (subset only), Day 15/ D01 (subset only), Day 29/Day 01, Month 6/Day 01, Year 1/Month 6, Year 2/Year 1, Year 3/Year 2
Percentage of participants with seroconversion to YF virus in all investigational vaccine groups 28 days after the co-administration of vYF with measlescontaining vaccine in the MMR group and at successive timepoints
Seroconversion rates will be assessed using a YF MN assay Seroconversion is defined as a 4-fold increase in NAb titers as compared to the prevaccination value
Measured: 28 days after the coadministration of MMR with vYF At Month 6 and yearly from Year 1 to Year 3
Percentage of participants with seroprotection to YF virus in all investigational vaccine groups 28 days after the co-administration of vYF with measlescontaining vaccine in the MMR group and at successive timepoints
Seroprotection is defined as NAb titers ≥ 10 (1/dil) at the corresponding timepoint
Measured: 28 days after the coadministration of MMR with vYF At Month 6 and yearly from Year 1 to Year 3
GMTs of neutralizing antibodies against YF virus in all investigational vaccine groups 28 days after the co-administration of vYF with measlescontaining vaccine in the MMR group and at successive timepoints
Antibody titers are expressed as geometric mean titers
Measured: 28 days after the coadministration of MMR with vYF At Month 6 and yearly from Year 1 to Year 3
GMTRs of neutralizing antibodies against YF virus in all investigational vaccine groups 28 days after the co-administration of vYF with measlescontaining vaccine in the MMR group and at successive timepoints
GMTRs Day 29/Day 01, Month 6/Day 01, Year 1/Month 6, Year 2/Year 1, Year 3/Year 2
Measured: 28 days after the coadministration of MMR with vYF At Month 6 and yearly from Year 1 to Year 3
Percentage of participants, by age group, with seroconversion to YF virus in all investigational vaccine groups before (Day 01) and after investigational vaccine administration at various timepoints
Seroconversion is defined for measles, mumps and rubella respectively in participants seronegative at baseline as an antibody titer reaching the following thresholds for seropositivity:
- Anti-measles antibody concentrations ≥ 255 mIU/mL
- Anti-mumps antibody concentrations ≥ 10 (AbU)/mL
- Anti-rubella antibody concentrations ≥ 10 IU/mL
Measured: Before and 28 days after the coadministration of MMR with vYF
Percentage of participants with seroprotection to MMR before and 28 days after the coadministration of MMR with vYF in the MMR group
Measured: Before and 28 days after the coadministration of MMR with vYF
GMTs of neutralizing antibodies against MMR virus before and 28 days after the coadministration of MMR with vYF in the MMR group
Antibody titers are expressed as geometric mean titers
Measured: Before and 28 days after the coadministration of MMR with vYF
GMTRs of neutralizing antibodies against MMR virus before and 28 days after the coadministration of MMR with vYF in the MMR group
GMTRs Day 29/Day 01
Measured: Before and 28 days after the coadministration of MMR with vYF
Percentage of participants with seroconversion to YF virus before the booster dose administration at Y3, then 10 days and 28 days after a vYF booster dose in the booster subset
Seroconversion rates will be assessed using a YF MN assay Seroconversion is defined as a 4-fold increase in NAb titers as compared to the prevaccination value
Measured: At Day 11 and Day 29 after booster dose
Percentage of participants with seroprotection to YF virus before the booster dose administration at Y3, then 10 days and 28 days after a vYF booster dose in the booster subset
Seroprotection is defined as NAb titers ≥ 10 (1/dil) at the corresponding timepoint
Measured: At Day 11 and Day 29 after booster dose
GMTs of neutralizing antibodies against YF virus before the booster dose administration at Y3, then 10 days and 28 days after a vYF booster dose in the booster subset
Antibody titers are expressed as geometric mean titers
Measured: At Day 11 and Day 29 after booster dose
GMTRs of neutralizing antibodies against YF virus before the booster dose administration at Y3, then 10 days and 28 days after a vYF booster dose in the booster subset
GMTRs Day 11/D01 and Day 29/Day 01
Measured: At Day 11 and Day 29 after booster dose
Percentage of participants with seroconversion to YF up to Day 29 will be described depending on the FV status at baseline (YF, Dengue, Zika) by age group
YF and Zika NAbs will be measured using a qualified MN assay Quantitation of human IgG antibodies against dengue virus (DENV) nonstructural protein 1 (NS1) in human sera will be determined using a qualified ELISA assay. Seroconversion is defined as a 4-fold increase in NAb titers as compared to the prevaccination value
Measured: Up to Day 29
Percentage of participants with seroprotection to YF up to Day 29 will be described depending on the FV status at baseline (YF, Dengue, Zika) by age group
Seroprotection is defined as NAb titers ≥ 10 (1/dil) at the corresponding timepoint
Measured: Up to Day 29
GMTs of neutralizing antibodies against YF up to Day 29 will be described depending on the FV status at baseline (YF, Dengue, Zika) by age group
Antibody titers are expressed as geometric mean titers
Measured: Up to Day 29
GMTRs of neutralizing antibodies against YF up to Day 29 will be described depending on the FV status at baseline (YF, Dengue, Zika) by age group
GMTRs Day 29/Day 01
Measured: Up to Day 29
Number of participants with immediate adverse events
Immediate adverse events are any unsolicited systemic adverse events reported in the 30 minutes after vaccination
Measured: Within 30 minutes after each vaccination
Number of participants with solicited injection site reactions
Solicited injection site reactions:
- for participants < 24 months include: injection site tenderness, injection site erythema, injection site swelling
- for participants aged ≥ 2 years and < 5 years include: injection site pain, injection site erythema and injection site swelling
Measured: Within 7 days after each vaccination
Number of participants with solicited systemic reactions
Solicited systemic reactions:
- for participants < 24 months include: fever, vomiting, crying abnormal, drowsiness, appetite lost, irritability
- for participants aged ≥ 2 years and < 5 years include: fever, headache, fatigue and myalgia
Measured: Within 14 days after each vaccination
Number of participants with unsolicited adverse events (AEs)
Unsolicited (spontaneously reported) AEs, not fulfilling criteria for solicited adverse reactions
Measured: Within 28 days after each vaccination
Number of participants with medically attended adverse events (MAAEs)
MAAEs will be collected as part of the unsolicited AEs
Measured: From Day 01 to Day 29
Number of participants with serious adverse events (SAEs) and adverse events of special interest (AESIs)
SAEs and AESIs
Measured: From Day 01 to Month 6 and from Year 3 to Year 3 + 6 Months for the booster subset
Hematology in a subset of participants 9-24 months of age and in a subset of participants aged 2-5 years
Blood samples will be taken for the determination of hematology
Measured: At Day 01 and at Day 05
Biochemistry in a subset of participants 9-24 months of age and in a subset of participants aged 2-5 years
Blood samples will be taken for the determination of biochemistry
Measured: At Day 01 and at Day 05
YF vaccinal viremia in each vaccine groups (vYF, Stamaril and YF-VAX) in a subset of participants 9-24 months of age
YF vaccinal viremia will be measured by YF-specific quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay
Measured: At Day 01 and at Day 05
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted5 Aug 2025
- Study start11 Jul 2025
- Primary completion28 Nov 2026 (estimated)
- Study completion4 Mar 2030 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Yellow Fever ImmunizationStudies of the same condition, open and under way.
- More trials run by SanofiThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
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 3
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 2,440 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Sanofi
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07103148
- Sponsor's protocol ID
- VYF04
- Other IDs
- VYF04, U1111-1300-4387
- Status last verified
- Oct 2026
- First submitted
- 7 Jul 2025
- Last updated
- 14 Oct 2026
- Results posted
- No
- 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
Study at a glance
From the registry record, last updated by the sponsor on 14 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Parallel Group, Phase III Randomized, Modified Double-blind, Active Controlled Study to Investigate the Immunogenicity and Safety of vYF Compared to Licensed YF Vaccines in Pediatric Population Aged 9 Months to 5 Years of Age
- ClinicalTrials.gov ID
- NCT07103148
- Acronym / sponsor ID
- VYF04
- Conditions
- Yellow Fever Immunization
- Keywords
- Yellow fever
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 2,440 participants (estimated)
- Lead sponsor
- SanofiIndustry (pharma, biotech, devices)
- Study start
- 11 Jul 2025 (actual)
- Primary completion
- 28 Nov 2026 (estimated)
- Study completion
- 4 Mar 2030 (estimated)
- First posted
- 5 Aug 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The purpose of this study is to determine whether vYF (investigational vaccine) is safe and can help the body to develop antibodies (immunogenicity) compared with Stamaril vaccine and YF-VAX vaccine (both licensed vaccines) and when they are co-administered with Measles Mumps Rubella (MMR) vaccines in infants aged 11-15 months.
Number of Participants:
A total of 2440 participants is planned to be enrolled in VYF04 study.
Study Arms and Duration:
Eligible participants will be randomized in 2 independent groups (9-24 months, 2-5 years) to receive 1 dose of either vYF or Stamaril or YF-VAX in a 2:1:1 ratio within each age group. An additional group with participants of 11-15 months of age will also receive at the same vaccination visit vYF and a single dose of MMR vaccine.
For the 2nd step (YF booster vaccine administration in a subset), at the Year (Y) 3 visit, a subset of 120 participants of the 9-24 months of age group who did receive a YF vaccine on Day(D) 01 will be invited to join a booster dose assessment (booster dose administered after the Y3 visit blood sample has been taken). Participants aged 11 to 15 months at the time of the concomitant administration of vYF and MMR will not be eligible for receiving a booster dose.
The duration of each participation will be approximately 3 years for all participants (including participants co-administered on D01 with vYF and MMR), and 6 more months post-booster dose administration for the participants enrolled in the booster subset.
Detailed description
The duration of each participant's participation will be up to approximately 3 years (not including booster phase in a subset)
The Phase III VYF04 is the first study to be carried out with the investigational vYF in pediatric populations.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 7
| Arm | Type | Receives |
|---|---|---|
| Group 1 (9-24 months) | Experimental | Biological: Yellow fever vaccine (live)Primary vaccination phase: 1 injection of vYF vaccine at Day 1 Booster phase: 1 injection of vYF vaccine at Year 3 (in a subset) |
| Group 2 (9-24 months) | Active comparator | Biological: Yellow fever vaccine (live)Primary vaccination phase: 1 injection of Stamaril vaccine at Day 1 Booster phase: 1 injection of Stamaril vaccine at Year 3 (in a subset) |
| Group 3 (9-24 months) | Active comparator | Biological: Yellow fever vaccine (live)Primary vaccination phase: 1 injection of YF-VAX vaccine at Day 1 Booster phase: 1 injection of YF-VAX vaccine at Year 3 (in a subset) |
| Group 4 (2-5 years) | Experimental | Biological: Yellow fever vaccine (live)Primary vaccination phase: 1 injection of vYF vaccine at Day 1 |
| Group 5 (2-5 years) | Active comparator | Biological: Yellow fever vaccine (live)Primary vaccination phase: 1 injection of Stamaril vaccine at Day 1 |
| Group 6 (2-5 years) | Active comparator | Biological: Yellow fever vaccine (live)Primary vaccination phase: 1 injection of YF-VAX vaccine at Day 1 |
| Group 7 (approximately 11-15 months) | Experimental | Biological: Yellow fever vaccine (live), Biological: Measles, combinations with mumps and rubella, live attenuatedPrimary vaccination phase: 1 injection of MMR vaccine at Day 1 in a cohort of 11 to 15 months of age vaccinated with vYF |
Who may qualify
- Ages
- 9 months to 5 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Child
Key inclusion criteria (9 listed)
- Aged 9 months to 5 years on the day of inclusion*
- Aged 11 to 15 months* on the day of inclusion for participants enrolled in the MMR co-administration group
- Participants who are healthy as determined by medical evaluation including medical history and physical examination
- For infants*, born after a gestation period of 27 through 36 weeks and medically stable as assessed by the investigator, based on the following definition: "Medically stable" refers to the condition of premature infants who do not require significant medical support or ongoing management for debilitating disease and who have demonstrated a clinical course of sustained recovery by the time they receive the first dose of study intervention
- Participant and parent/LAR are able to attend all scheduled visits and to comply with all study procedures
Key exclusion criteria (20 listed)
- Known or suspected congenital or acquired immunodeficiency; or receipt of immunosuppressive therapy, such as anti-cancer chemotherapy irradiation 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 FV infection
- Known systemic hypersensitivity to any of the study intervention components, eggs or history of a life-threatening reaction to the study interventions used in the study or to a product containing any of the same substances
- Moderate or severe acute illness/infection (according to Investigator judgment) or febrile illness (temperature ≥ 38.0°C [≥ 100.4°F]) on the day of study intervention administration. A prospective participant should not be included in the study until the condition has resolved or the febrile event has subsided.
- Chronic illness* that, in the opinion of the Investigator, is at a stage where it might interfere with study conduct or completion , including malignancy, such as leukemia, or lymphoma
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Yellow fever vaccine (live)Also: vYF vaccinePowder and diluent for suspension for injection Subcutaneous | Biological | Group 1 (9-24 months), Group 4 (2-5 years), Group 7 (approximately 11-15 months) |
| Yellow fever vaccine (live)Also: Stamaril vaccinePowder and diluent for suspension for injection Subcutaneous | Biological | Group 2 (9-24 months), Group 5 (2-5 years) |
| Yellow fever vaccine (live)Also: YF-VAX vaccinePowder and diluent for suspension for injection Subcutaneous | Biological | Group 3 (9-24 months), Group 6 (2-5 years) |
| Measles, combinations with mumps and rubella, live attenuatedAlso: MMR II vaccinePowder, lyophilized, for suspension for reconstitution Subcutaneous or intermuscular | Biological | Group 7 (approximately 11-15 months) |
Primary outcome
Percentage of participants with seroconversion to YF virus after 1 dose of vYF compared to seroconversion after 1 dose of the Stamaril in YF-naive participants (9-24 months)
Time frame: At Day 29, 28 days post-vaccination (on Day 01) with vYF or Stamaril
Seroconversion rates will be assessed using a YF MN assay Seroconversion is defined as a 4-fold increase in NAb titers as compared to the pre-vaccination value
Percentage of participants with seroconversion to YF virus after 1 dose of vYF compared to seroconversion after 1 dose of the YF-VAX in YF-naive participants (9-24 months)
Time frame: At Day 29, 28 days post-vaccination (on Day 01) with vYF or YF-VAX
Seroconversion rates will be assessed using a YF MN assay Seroconversion is defined as a 4-fold increase in NAb titers as compared to the pre-vaccination value
Percentage of participants with seroconversion to YF virus after 1 dose of vYF compared to seroconversion after 1 dose of the Stamaril in YF-naive participants (2-5 years)
Time frame: At Day 29, 28 days post-vaccination (on Day 01) with vYF or Stamaril
Seroconversion rates will be assessed using a YF MN assay Seroconversion is defined as a 4-fold increase in NAb titers as compared to the pre-vaccination value
Percentage of participants with seroconversion to YF virus after 1 dose of vYF compared to seroconversion after 1 dose of the YF-VAX in YF-naive participants (2-5 years)
Time frame: At Day 29, 28 days post-vaccination (on Day 01) with vYF or YF-VAX
Seroconversion rates will be assessed using a YF MN assay Seroconversion is defined as a 4-fold increase in NAb titers as compared to the pre-vaccination value
29 secondary outcomes
Percentage of participants, by age group, with seroconversion to YF virus in all investigational vaccine groups before (Day 01) and after investigational vaccine administration at various timepoints
Time frame: At Day 01 and at Day 11 (in a subset), Day 15 (in a subset), Day 29, Month 6, and yearly from Year 1 to Year 3
Percentage of participants, by age group, with seroprotection to YF virus in all investigational vaccine groups before (Day 01) and after investigational vaccine administration at various timepoints
Time frame: At Day 01 and at Day 11 (in a subset), Day 15 (in a subset), Day 29, Month 6, and yearly from Year 1 to Year 3
Geometric Mean Titers (GMTs) of neutralizing antibodies against YF virus in all investigational vaccine groups, by age group, before (Day 01) and after investigational vaccine administration at various timepoints
Time frame: At Day 01 and at Day 11 (in a subset), Day 15 (in a subset), Day 29, Month 6, and yearly from Year 1 to Year 3
Geometric Mean Titers Ratio (GMTRs) of neutralizing antibodies against YF virus in all investigational vaccine groups, by age group, before (Day 01) and after investigational vaccine administration at various timepoints
Time frame: GMTRs Day 11/Day 01 (subset only), Day 15/ D01 (subset only), Day 29/Day 01, Month 6/Day 01, Year 1/Month 6, Year 2/Year 1, Year 3/Year 2
Percentage of participants with seroconversion to YF virus in all investigational vaccine groups 28 days after the co-administration of vYF with measlescontaining vaccine in the MMR group and at successive timepoints
Time frame: 28 days after the coadministration of MMR with vYF At Month 6 and yearly from Year 1 to Year 3
Percentage of participants with seroprotection to YF virus in all investigational vaccine groups 28 days after the co-administration of vYF with measlescontaining vaccine in the MMR group and at successive timepoints
Time frame: 28 days after the coadministration of MMR with vYF At Month 6 and yearly from Year 1 to Year 3
GMTs of neutralizing antibodies against YF virus in all investigational vaccine groups 28 days after the co-administration of vYF with measlescontaining vaccine in the MMR group and at successive timepoints
Time frame: 28 days after the coadministration of MMR with vYF At Month 6 and yearly from Year 1 to Year 3
GMTRs of neutralizing antibodies against YF virus in all investigational vaccine groups 28 days after the co-administration of vYF with measlescontaining vaccine in the MMR group and at successive timepoints
Time frame: 28 days after the coadministration of MMR with vYF At Month 6 and yearly from Year 1 to Year 3
Percentage of participants, by age group, with seroconversion to YF virus in all investigational vaccine groups before (Day 01) and after investigational vaccine administration at various timepoints
Time frame: Before and 28 days after the coadministration of MMR with vYF
Percentage of participants with seroprotection to MMR before and 28 days after the coadministration of MMR with vYF in the MMR group
Time frame: Before and 28 days after the coadministration of MMR with vYF
GMTs of neutralizing antibodies against MMR virus before and 28 days after the coadministration of MMR with vYF in the MMR group
Time frame: Before and 28 days after the coadministration of MMR with vYF
GMTRs of neutralizing antibodies against MMR virus before and 28 days after the coadministration of MMR with vYF in the MMR group
Time frame: Before and 28 days after the coadministration of MMR with vYF
Percentage of participants with seroconversion to YF virus before the booster dose administration at Y3, then 10 days and 28 days after a vYF booster dose in the booster subset
Time frame: At Day 11 and Day 29 after booster dose
Percentage of participants with seroprotection to YF virus before the booster dose administration at Y3, then 10 days and 28 days after a vYF booster dose in the booster subset
Time frame: At Day 11 and Day 29 after booster dose
GMTs of neutralizing antibodies against YF virus before the booster dose administration at Y3, then 10 days and 28 days after a vYF booster dose in the booster subset
Time frame: At Day 11 and Day 29 after booster dose
GMTRs of neutralizing antibodies against YF virus before the booster dose administration at Y3, then 10 days and 28 days after a vYF booster dose in the booster subset
Time frame: At Day 11 and Day 29 after booster dose
Percentage of participants with seroconversion to YF up to Day 29 will be described depending on the FV status at baseline (YF, Dengue, Zika) by age group
Time frame: Up to Day 29
Percentage of participants with seroprotection to YF up to Day 29 will be described depending on the FV status at baseline (YF, Dengue, Zika) by age group
Time frame: Up to Day 29
GMTs of neutralizing antibodies against YF up to Day 29 will be described depending on the FV status at baseline (YF, Dengue, Zika) by age group
Time frame: Up to Day 29
GMTRs of neutralizing antibodies against YF up to Day 29 will be described depending on the FV status at baseline (YF, Dengue, Zika) by age group
Time frame: Up to Day 29
Number of participants with immediate adverse events
Time frame: Within 30 minutes after each vaccination
Number of participants with solicited injection site reactions
Time frame: Within 7 days after each vaccination
Number of participants with solicited systemic reactions
Time frame: Within 14 days after each vaccination
Number of participants with unsolicited adverse events (AEs)
Time frame: Within 28 days after each vaccination
Number of participants with medically attended adverse events (MAAEs)
Time frame: From Day 01 to Day 29
Number of participants with serious adverse events (SAEs) and adverse events of special interest (AESIs)
Time frame: From Day 01 to Month 6 and from Year 3 to Year 3 + 6 Months for the booster subset
Hematology in a subset of participants 9-24 months of age and in a subset of participants aged 2-5 years
Time frame: At Day 01 and at Day 05
Biochemistry in a subset of participants 9-24 months of age and in a subset of participants aged 2-5 years
Time frame: At Day 01 and at Day 05
YF vaccinal viremia in each vaccine groups (vYF, Stamaril and YF-VAX) in a subset of participants 9-24 months of age
Time frame: At Day 01 and at Day 05
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 14 Oct 2026.
- VYF04 Plain Language Results SummaryLink provided by the sponsor.
- Individual participant dataSharing planned: 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
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Trial Transparency email recommended (Toll free for US & Canada) contact
15 sites in 3 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing Yellow fever vaccine (live) and Measles, combinations with mumps and rubella, live attenuated in people with Yellow Fever Immunization, run by Sanofi at 15 sites in 3 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 9 inclusion and 20 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: looking for participants now, as of the sponsor's last update on 14 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 15 sites in Mexico, Honduras, Panama. 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 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Trial Transparency email recommended (Toll free for US & Canada) (800-633-1610 ext. option 6, Contact-US@sanofi.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Percentage of participants with seroconversion to YF virus after 1 dose of vYF compared to seroconversion after 1 dose of the Stamaril in YF-naive participants (9-24 months) (time frame: At Day 29, 28 days post-vaccination (on Day 01) with vYF or Stamaril). The study lists 4 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
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 14 Oct 2026.