A Phase 2 interventional study of Yellow fever vaccine (produced on serum-free Vero cells) and Yellow fever vaccine in Yellow Fever and Healthy Volunteers, sponsored by Sanofi Pasteur, a Sanofi Company. Active, not recruiting at 11 sites in United States. Open to participants aged 18 Years to 60 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-03.
Sponsored by Sanofi Pasteur, a Sanofi Company (part of Sanofi) · Phase 2, Interventional, and Prevention
The primary objective of the study is to demonstrate the non-inferiority of the antibody response in terms of seroconversion rate 28 days after vaccine administration of one dose of yellow fever vaccine (vYF) compared to the antibody response after one dose of the YF-VAX control vaccine in yellow fever naïve participants.
The secondary objectives of the study are:
The duration of each participant's participation will be approximately 5 years.
52 studies on the registry are indexed under Yellow Fever; 10 are open to participants now.
This study's enrollment of 568 is above the median of 112 across 43 interventional studies indexed under Yellow Fever.
Browse Yellow Fever studies →Sanofi Pasteur, a Sanofi Company is the lead sponsor of 374 studies on the registry; 4 are open to participants now.
Of its 94 completed or terminated interventional studies of FDA-regulated products, 73 (78%) have results posted.
First submitted after Sanofi Pasteur became part of Sanofi.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Is of non-. To be considered of non-childbearing potential, a female must be for at least 1 year, or surgically sterile.
OR Is of childbearing potential and agrees to use an effective method or abstinence from at least 4 weeks prior to vaccination until at least 4 weeks after vaccination. A 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 will be repeated on Day 29 to confirm the participant is still not pregnant within the 28 days of vaccine administration.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Postmenopausal
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
1 injection of vYF at Day 1
Biological: Yellow fever vaccine (produced on serum-free Vero cells)
1 injection of YF-VAX at Day 1
Biological: Yellow fever vaccine
Powder and diluent for suspension for injection Subcutaneous injection
Powder and diluent for suspension for injection Subcutaneous injection
Also known as: YF-VAX
Percentage of Yellow Fever (YF)-Naive Participants Who Achieved Seroconversion 28 Days Post Dose 1
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 antibody (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.
Time frame: 28 days post dose 1 (Day 29)
Percentage of Participants Who Achieved Seroconversion
Seroconversion was defined as a 4-fold increase in Nab titers as compared to the pre-vaccination value: compared to the Day 1 titers at each timepoint up to Month 6; and 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.
Time frame: Days 1, 11, 29, Month 6, Years 1 and 2
Percentage of Participants Who Achieved Seroprotection
Seroprotection was defined as NAb titers \>=threshold of 10 (1/dilution). The YF NAb titers were determined using a validated live virus MN assay. Percentages are rounded off to the tenth decimal place.
Time frame: Days 1, 11, 29, Month 6, Years 1 and 2
Geometric Mean Titers (GMTs) of Antibodies Against Yellow Fever Virus
GMTs of antibody against YF virus was measured using a validated live virus MN assay.
Time frame: Days 1, 11, 29, Month 6, Years 1 and 2
Geometric Mean Titers Ratio (GMTRs) of Antibodies Against Yellow Fever Virus
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.
Time frame: Days 1, 11, 29, Month 6, Years 1 and 2
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.
Time frame: Up to 30 minutes post vaccination on Day 1
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.
Time frame: Up to 7 days post vaccination (Day 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.
Time frame: Up to 14 days post vaccination (Day 15)
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.
Time frame: Up to 28 days post vaccination (Day 29)
Number of Participants With 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.
Time frame: From the first dose of study vaccine administration (Day 1) up to 6 months post vaccination, approximately up to Day 181
Number of Participants With Serious Adverse Events and Deaths up to Day 1155
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.
Time frame: From the first dose of study vaccine administration (Day 1) up to DBL date of 29 August 2024, approximately up to Day 1155
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.
Time frame: From the first dose of study vaccine administration (Day 1) up to end of study, approximately 5 years
Number of Participants With Out-of-Range Biochemistry Parameters
Blood samples were collected at specified timepoints for assessment of biochemistry parameters: alanine aminotransferase (ALT), aspartate transaminase (AST), creatine phosphokinase (CPK), alkaline phosphatase (ALP), bilirubin (accompanied by any increase in liver function test (LFT) and normal LFT), creatinine and C-reactive protein (CRP). The intensity grading scale for laboratory abnormalities was pre-specified in the protocol. Number of participants with out-of-range biochemistry parameters are presented.
Time frame: Days 1 and 11
Number of Participants With Out-of-Range Hematology Parameters
Blood samples were collected at specified timepoints for assessment of hematology parameters: red blood cell count (RBC), hematocrit, mean corpuscular volume (MCV), monocytes, basophils, hemoglobin (Hb), white blood cell count (WBC) (increase and decrease), neutrophils and lymphocytes (decrease), eosinophils, platelets (decrease). The intensity grading scale for laboratory abnormalities was pre-specified in the protocol. Number of participants with out-of-range hematology parameters are presented.
Time frame: Days 1 and 11
This study was conducted at 11 sites in the United States of America from 01 July 2021 to 27 May 2022. Interim results are presented up to Year 2 follow-up, data base lock (DBL) date of 29 August 2024.
| Milestone | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Started | 382 | 186 |
| Randomized and vaccinated | 379 | 186 |
| Completed | 294 | 150 |
| Not completed | 88 | 36 |
| Withdrew: Adverse event | 0 | 1 |
| Withdrew: Protocol deviation | 4 | 1 |
| Withdrew: Withdrawal by subject | 5 | 2 |
| Withdrew: Lost to follow-up | 16 | 7 |
| Withdrew: Ongoing at the time of dbl date | 60 | 25 |
| Withdrew: Randomized but did not receive vaccination | 3 | 0 |
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 antibody (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.
| percentage of participants | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Percentage of Yellow Fever (YF)-Naive Participants Who Achieved Seroconversion 28 Days Post Dose 1 | 99.7 (98.3 to 100) | 99.4 (96.5 to 100) |
Seroconversion was defined as a 4-fold increase in Nab titers as compared to the pre-vaccination value: compared to the Day 1 titers at each timepoint up to Month 6; and 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.
| percentage of participants | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Day 11 | 30.5 (19.2 to 43.9) | 58.1 (39.1 to 75.5) |
| Day 29 | 97.8 (95.8 to 99.1) | 98.4 (95.3 to 99.7) |
| Month 6 | 94.7 (91.7 to 96.8) | 98.8 (95.8 to 99.9) |
| Year 1 | 4.4 (2.5 to 7.3) | 4.9 (2.1 to 9.4) |
| Year 2 | 1.4 (0.4 to 3.5) | 1.3 (0.2 to 4.7) |
Seroprotection was defined as NAb titers \>=threshold of 10 (1/dilution). The YF NAb titers were determined using a validated live virus MN assay. Percentages are rounded off to the tenth decimal place.
| percentage of participants | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Day 1 | 6.2 (4.0 to 9.2) | 4.4 (1.9 to 8.4) |
| Day 11 | 39.0 (26.5 to 52.6) | 61.3 (42.2 to 78.2) |
| Day 29 | 99.5 (98.1 to 99.9) | 99.5 (97.0 to 100) |
| Month 6 | 98.8 (97.0 to 99.7) | 99.4 (96.8 to 100) |
| Year 1 | 97.5 (95.1 to 98.9) | 97.5 (93.8 to 99.3) |
| Year 2 | 98.6 (96.6 to 99.6) | 100 (97.6 to 100) |
GMTs of antibody against YF virus was measured using a validated live virus MN assay.
| titer | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Day 1 | 5.87 (5.43 to 6.35) | 5.56 (5.11 to 6.05) |
| Day 11 | 15.2 (9.69 to 23.7) | 42.6 (20.4 to 88.9) |
| Day 29 | 2540 (2218 to 2909) | 3004 (2495 to 3616) |
| Month 6 | 544 (467 to 633) | 702 (572 to 861) |
| Year 1 | 405 (342 to 480) | 552 (438 to 696) |
| Year 2 | 196 (169 to 226) | 245 (200 to 301) |
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.
| ratio | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Day 11/Day 1 | 2.16 (1.49 to 3.12) | 5.57 (2.96 to 10.5) |
| Day 29/Day 1 | 227 (194 to 264) | 280 (227 to 344) |
| Month 6/Day 1 | 49.6 (42.3 to 58.1) | 66.3 (53.7 to 81.8) |
| Year 1/Month 6 | 0.742 (0.661 to 0.832) | 0.777 (0.658 to 0.916) |
| Year 2/Year 1 | 0.473 (0.426 to 0.524) | 0.426 (0.367 to 0.495) |
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.
| Participants | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Number of Participants With Unsolicited Systemic Adverse Events (AEs) | 1 | 0 |
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.
| Participants | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Number of Participants With Solicited Injection Site Reactions | 115 | 64 |
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.
| Participants | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Number of Participants With Solicited Systemic Reactions | 178 | 102 |
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.
| Participants | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Number of Participants With Unsolicited Adverse Events | 99 | 40 |
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.
| Participants | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| SAEs | 6 | 2 |
| AESIs | 0 | 0 |
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.
| Participants | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| SAEs | 6 | 5 |
| Deaths | 2 | 1 |
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.
Results for this outcome have not been posted.
Blood samples were collected at specified timepoints for assessment of biochemistry parameters: alanine aminotransferase (ALT), aspartate transaminase (AST), creatine phosphokinase (CPK), alkaline phosphatase (ALP), bilirubin (accompanied by any increase in liver function test (LFT) and normal LFT), creatinine and C-reactive protein (CRP). The intensity grading scale for laboratory abnormalities was pre-specified in the protocol. Number of participants with out-of-range biochemistry parameters are presented.
| Participants | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Day 1: ALT | 4 | 0 |
| Day 11: ALT | 6 | 1 |
| Day 1: AST | 3 | 0 |
| Day 11: AST | 5 | 2 |
| Day 1: CPK | 9 | 6 |
| Day 11: CPK | 7 | 6 |
| Day 1: ALP | 3 | 0 |
| Day 11: ALP | 2 | 0 |
| Day 1: Bilirubin (Any increase in LFT) | 0 | 0 |
| Day 11: Bilirubin (Any increase in LFT) | 0 | 0 |
| Day 1: Bilirubin (Normal LFT) | 1 | 1 |
| Day 11: Bilirubin (Normal LFT) | 1 | 1 |
| Day 1: Creatinine | 4 | 2 |
| Day 11: Creatinine | 8 | 2 |
| Day 1: CRP | 4 | 4 |
| Day 11: CRP | 5 | 4 |
Blood samples were collected at specified timepoints for assessment of hematology parameters: red blood cell count (RBC), hematocrit, mean corpuscular volume (MCV), monocytes, basophils, hemoglobin (Hb), white blood cell count (WBC) (increase and decrease), neutrophils and lymphocytes (decrease), eosinophils, platelets (decrease). The intensity grading scale for laboratory abnormalities was pre-specified in the protocol. Number of participants with out-of-range hematology parameters are presented.
| Participants | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Day 1: RBC | 7 | 4 |
| Day 11: RBC | 11 | 5 |
| Day 1: Hematocrit | 12 | 6 |
| Day 11: Hematocrit | 10 | 5 |
| Day 1: MCV | 7 | 3 |
| Day 11: MCV | 5 | 2 |
| Day 1: Monocytes | 6 | 1 |
| Day 11: Monocytes | 6 | 4 |
| Day 1: Basophils | 0 | 0 |
| Day 11: Basophils | 0 | 0 |
| Day 1: Hb | 12 | 7 |
| Day 11: Hb | 10 | 6 |
| Day 1: WBC increase | 2 | 1 |
| Day 11: WBC increase | 13 | 0 |
| Day 1: WBC decrease | 2 | 1 |
| Day 11: WBC decrease | 13 | 0 |
| Day 1: Neutrophils decrease | 2 | 1 |
| Day 11: Neutrophils decrease | 8 | 3 |
| Day 1: Lymphocytes decrease | 0 | 0 |
| Day 11: Lymphocytes decrease | 2 | 1 |
| Day 1: Eosinophils | 1 | 2 |
| Day 11: Eosinophils | 1 | 2 |
| Day 1: Platelets decrease | 4 | 1 |
| Day 11: Platelets decrease | 5 | 0 |
Collected over AEs, SAEs and all-cause mortality (deaths) were collected from the first dose of study vaccine administration (Day 1) up to DBL date of 29 August 2024, approximately up to Day 1155. Non-serious events are listed at a 5% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| vYF 0.5 mL | 2/379 (0.5%) | 6/379 (1.6%) | 206/379 (54.4%) |
| YF-VAX 0.5 mL | 1/186 (0.5%) | 5/186 (2.7%) | 113/186 (60.8%) |
| Event | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| Blood Loss AnaemiaBlood and lymphatic system disorders | 0/379 | 1/186 |
| Atrial FibrillationCardiac disorders | 0/379 | 1/186 |
| DeathGeneral disorders | 0/379 | 1/186 |
| AppendicitisInfections and infestations | 0/379 | 1/186 |
| Pelvic FractureInjury, poisoning and procedural complications | 0/379 | 1/186 |
| OverdoseInjury, poisoning and procedural complications | 2/379 | 0/186 |
| Abdominal Pain UpperGastrointestinal disorders | 1/379 | 0/186 |
| CellulitisInfections and infestations | 1/379 | 0/186 |
| Flank PainMusculoskeletal and connective tissue disorders | 1/379 | 0/186 |
| Suicidal IdeationPsychiatric disorders | 1/379 | 0/186 |
| Event | vYF 0.5 mL | YF-VAX 0.5 mL |
|---|---|---|
| HeadacheNervous system disorders | 134/379 | 70/186 |
| MalaiseGeneral disorders | 110/379 | 63/186 |
| MyalgiaMusculoskeletal and connective tissue disorders | 114/379 | 59/186 |
| Injection Site PainGeneral disorders | 105/379 | 58/186 |
| Injection Site ErythemaGeneral disorders | 27/379 | 8/186 |
The randomized population included all participants with data in the case report form (CRF).
| Age, Continuous(years) | vYF 0.5 mL | YF-VAX 0.5 mL | Total |
|---|---|---|---|
| Mean | 40.0 ± 11.87 | 39.3 ± 11.88 | 39.7 ± 11.87 |
| Sex: Female, Male(Participants) | vYF 0.5 mL | YF-VAX 0.5 mL | Total |
|---|---|---|---|
| Female | 234 | 116 | 350 |
| Male | 148 | 70 | 218 |
| Race/Ethnicity, Customized(Participants) | vYF 0.5 mL | YF-VAX 0.5 mL | Total |
|---|---|---|---|
| American Indian or Alaska Native | 4 | 2 | 6 |
| Asian | 15 | 12 | 27 |
| Black or African American | 93 | 53 | 146 |
| Native Hawaiian or Other Pacific Islander | 0 | 1 | 1 |
| White | 258 | 112 | 370 |
| Multiple origin | 6 | 2 | 8 |
| Not Reported | 5 | 1 | 6 |
| Unknown | 1 | 3 | 4 |
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: 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
Ran from Jul 2021 to primary completion in Jun 2022, 11 months.
Results were first posted in Jun 2025, 2 years 11 months after primary completion. A results delay was requested in Jun 2023.
How these figures are worked out, and which studies are left out of them.
This study is active, not recruiting, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Yellow Fever Vaccine
Sanofi Pasteur, a Sanofi Company →