Respiratory Syncytial Virus InfectionPhase 1/2VAD00001NCT04491877
Study of an Live-Attenuated Respiratory Syncytial Virus Vaccine in Infants and Toddlers
A Phase 1/2 study testing RSV vaccine formulation 1 and RSV vaccine formulation 2 in people with Respiratory Syncytial Virus Infection, run by Sanofi Pasteur, a Sanofi Company at 29 sites in 3 countries.
Trial summary
The primary objectives of the study were: To assess the safety profile of each dose of the study product after each and any administration in all infants and toddlers regardless of baseline serostatus. Read more about this study
- Who is it for?
- Ages 6 to 18 monthsHealthy volunteers can take part
- Conditions the study is for
- Respiratory Syncytial Virus Infection
- What is being tested?
- RSV vaccine formulation 1 and RSV vaccine formulation 2
- Type of treatment
- Vaccines
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 259 participants
- Where
- 29 sitesin 3 countries
- Study dates
- 17 Sep 2020to 13 Apr 2023
- Phase
- Phase 1/2
- 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 6 to 18 months
- All sexes
- Healthy volunteers accepted
- Child
Who may be able to join
- Aged 6 through 18 months at Day 0.
- Informed consent form has been signed and dated by the parent(s) or other legally acceptable representative (and by independent witness if required by local regulations).
- Participant and parent / guardian / legally acceptable representative are able to attend all scheduled visits and to comply with all trial procedures
Who cannot join
- Born at less than 34 weeks gestation
- Born at less than 37 weeks gestation and less than 1 year of age at the time
- 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).
- Probable or confirmed case of Coronavirus Disease 2019 (COVID-19).
- Known systemic hypersensitivity to any of the vaccine components, or history of a life-threatening reaction to the vaccine used in the trial or to a vaccine containing any of the same substances
- Any chronic illness
Show all 42Show fewer
- Chronic illness may include, but is not limited to, cardiac disorders, lung disease (including any history of reactive airway disease, receipt of bronchodilator therapy, or medically diagnosed wheezing), renal disorders, auto-immune disorders, diabetes, psychomotor diseases, and known congenital or genetic diseases
- Any history of medically diagnosed wheezing
- Any acute febrile, respiratory or gastrointestinal illness in the past 24 hours that according to investigator judgment is significant enough to interfere with successful inoculation on the day of vaccination. A prospective participant should not be included in the study until the condition has resolved or the febrile event has subsided
- Any previous anaphylactic reaction
- Current suspected or documented developmental disorder, delay, or other developmental problem
- Receipt of any of the following vaccines prior to enrollment:
- any influenza vaccine within 7 days prior, or
- any inactivated vaccine or live-attenuated rotavirus vaccine within the 14 days prior, or
- any live vaccine, other than rotavirus vaccine, within the 28 days prior, or
- another investigational vaccine or investigational drug within 28 days prior
- Previous receipt of a licensed or investigational RSV vaccine or previous receipt or planned administration of any anti-RSV product (such as ribavirin or RSV immune immune globulins [IG] or RSV monoclonal antibody)
- Receipt of immune globulins, blood or blood-derived products in the past 6 months prior to enrolment
- Receipt of any of the following medications within 3 days prior to study enrollment (Day 0):
- systemic antibacterial, antiviral, antifungal, anti-parasitic, or antituberculous agents, whether for treatment or prophylaxis, or
- intranasal medications, or
- other prescription medication except as permitted concomitant medications (prescription or non-prescription) including nutritional supplements, medications for gastroesophageal reflux, eye drops, and topical medications, including (but not limited to) cutaneous (topical) steroids, topical antibiotics, and topical antifungal agents
- Receipt of salicylate (aspirin) or salicylate-containing products within the 28 days prior to enrollment (Day 0)
- Any previous vaccine-associated adverse reaction that was Grade 3 or above. Note: if grading is not possible, determine if the reaction was considered severe or life threatening; if so, it is exclusionary.
- Scheduled administration of the following after planned inoculation:
- any influenza vaccine within 7 days after, or
- inactivated vaccine or live-attenuated rotavirus vaccine within the 14 days after, or
- any live vaccine other than rotavirus in the 28 days after, or
- another investigational vaccine or investigational drug in the 56 days after.
- Any previous receipt of supplemental oxygen therapy in a home or hospital setting, except the temporary receipt of supplemental oxygen for transient tachypnea in newborn
- Member of a household that contains an immunocompromised individual, including, but not limited to:
- a person who is HIV infected
- a person who has received chemotherapy within the 12 months prior to enrollment
- a person receiving immunosuppressant agents
- a person living with a solid organ or bone marrow transplant
- Participation at the time of study enrollment (or in the 6 weeks preceding the first trial vaccination) or planned participation during the present trial period in another clinical trial investigating a vaccine, drug, medical device, or medical procedure
- Member of a household that contains, or will contain, an infant who is less than 6 months of age at the enrollment date (or in the 6 weeks preceding the first trial vaccination) through Day 28
- Member of a household that contains another child/other children who is/are, or is/are scheduled to be, enrolled in this study in the same year AND the date of enrollment will not be concurrent with the other participant(s) living in the household (i.e., all eligible children from the same household must be enrolled on the same date)
- Attends a daycare facility and shares a daycare room with infants less than 6 months of age, and parent/guardian is unable or unwilling to suspend daycare for 28 days following inoculation
- Deprived of freedom in an emergency setting or hospitalized involuntarily
- Identified as a natural or adopted child of the Investigator or employee with direct involvement in the proposed study
- The above information was not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.
Trial locations and contacts
29 sites in 3 countries.
29 sites in 3 countries
United States25 sites
MedPharmics Inc-Site Number:8400040
Albuquerque, New Mexico, 87102
Elite Clinical Trials, Inc.-Site Number:8400001
Blackfoot, Idaho, 83221
Coastal Pediatric Research-Site Number:8400031
Charleston, South Carolina, 29414
Pediatric Associates of Charlottesville North-Site Number:8400007
Charlottesville, Virginia, 22911
Benchmark Research-Site Number:8400006
Covington, Louisiana, 70433
Alliance for Multispeciality Research-Site Number:8400014
El Dorado, Kansas, 67042
Matrix Clinical Research-Site Number:8400012
Gardena, California, 90247
East Carolina University/Brody Medical Sciences Building-Site Number:8400043
Greenville, North Carolina, 27834
Tribe Clinical Research-Site Number:8400027
Greenville, South Carolina, 29607
Leavitt Clinical Research-Site Number:8400036
Idaho Falls, Idaho, 83404
Snake River Research-Site Number:8400022
Idaho Falls, Idaho, 83404
Paradigm Clinical Research-Site Number:8400026
La Mesa, California, 91942
FMC Science-Site Number:8400042
Lampasas, Texas, 76550-1820
Michael W. Simon, MD, PSC-Site Number:8400013
Lexington, Kentucky, 40517
Be Well Clinical Studies-Site Number:8400054
Lincoln, Nebraska, 68516
Matrix Clinical Research-Site Number:8400032
Los Angeles, California, 90057
Clinical Research Institute-Site Number:8400053
Minneapolis, Minnesota, 55402
Boeson Research-Site Number:8400011
Missoula, Montana, 59804
Nola Research Works-Site Number:8400017
New Orleans, Louisiana, 70125
AMR - Newton-Site Number:8400002
Newton, Kansas, 67114
Meridian Clinical Research - Norfolk-Site Number:8400005
Norfolk, Nebraska, 68701
National Clinical Research Inc-Site Number:8400004
Richmond, Virginia, 23294
JBR Clinical Research-Site Number:8400041
Salt Lake City, Utah, 84107
California Research Foundation-Site Number:8400016
San Diego, California, 92123-1881
The South Bend Clinic Center for Research-Site Number:8400024
South Bend, Indiana, 46617
Chile2 sites
Investigational Site Number :1520001
Santiago, Reg Metropolitana de Santiago, 8380453
Investigational Site Number :1520004
Santiago, Reg Metropolitana de Santiago, 8420383
Honduras2 sites
Investigational Site Number :3400001
San Pedro Sula, 21104
Investigational Site Number :3400002
Tegucigalpa, 11101
About this study
Official title: Safety, Immunogenicity, Infectivity, and Dose-Finding Study of an Investigational Live-Attenuated Respiratory Syncytial Virus (RSV) Vaccine in Infants and Toddlers
The primary objectives of the study were:
- To assess the safety profile of each dose of the study product after each and any administration in all infants and toddlers regardless of baseline serostatus.
- To characterize the Respiratory Syncytial Virus (RSV) A serum neutralizing antibody responses to the study product in each vaccine group after vaccination in RSV-naïve participants.
Read more
The secondary objectives of the study were:
- To quantify the amount of vaccine virus shed by each participant by baseline serostatus.
- To determine the proportion of vaccinated infants and toddlers in each vaccine group infected with the vaccine virus at D56 (56 days after vaccination 1) for Cohorts 1, 2, 3 and 4, and at Day 84 (28 days after vaccination 2) for Cohorts 2 and 4 by baseline serostatus.
- To characterize the RSV A serum neutralizing antibody responses to the study product in each vaccine group after vaccination in RSV-experienced participants.
- To characterize serum RSV anti-F immunoglobulin G (IgG) antibody responses to the study product in each vaccine group after vaccination by baseline serostatus.
- To characterize serum RSV antibody responses (RSV A-neutralizing and anti-RSV F IgG) to the study product in each vaccine group after the RSV surveillance season or at least 5 months after the last vaccine administration by baseline serostatus.
Read the detailed description
Study duration per participant was maximum 12 months
- Conditions
- Respiratory Syncytial Virus Infection
- Being tested
- RSV vaccine formulation 1, RSV vaccine formulation 2, Placebo
- Medical subject headings
- Respiratory Syncytial Virus Infections
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
RSV vaccine formulation 1Biological
Pharmaceutical form: Suspension of virus Route of administration: Intranasal
RSV vaccine formulation 2Biological
Pharmaceutical form: Suspension of virus Route of administration: Intranasal
PlaceboBiological
Pharmaceutical form: Suspension Route of administration: Intranasal
| Study group | Role | What they receive |
|---|---|---|
| Cohort 1 (RSV vaccine formulation 1) | Experimental | 1 administration of RSV vaccine formulation 1 on Day 0 Receives: Biological: RSV vaccine formulation 1 |
| Cohort 1 (Placebo) | Placebo comparator | 1 administration of placebo on Day 0 Receives: Biological: Placebo |
| Cohort 2 (RSV vaccine formulation 1) | Experimental | 2 administrations of RSV vaccine formulation 1 on Day 0 and Day 56 Receives: Biological: RSV vaccine formulation 1 |
| Cohort 2 (Placebo) | Placebo comparator | 2 administrations of placebo on Day 0 and Day 56 Receives: Biological: Placebo |
| Cohort 3 (RSV vaccine formulation 2) | Experimental | 1 administration of RSV vaccine formulation 2 on Day 0 Receives: Biological: RSV vaccine formulation 2 |
| Cohort 3 (Placebo) | Placebo comparator | 1 administration of placebo on Day 0 Receives: Biological: Placebo |
| Cohort 4 (RSV vaccine formulation 1) | Experimental | 2 administrations of RSV vaccine formulation 1 on Day 0 and Day 56 Receives: Biological: RSV vaccine formulation 1 |
| Cohort 4 (RSV vaccine formulation 2) | Experimental | 2 administrations of RSV vaccine formulation 2 on Day 0 and Day 56 Receives: Biological: RSV vaccine formulation 2 |
| Cohort 4 (Placebo) | Placebo comparator | 2 administrations of placebo on Day 0 and Day 56 Receives: Biological: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Number of Participants With Immediate Unsolicited Systemic Adverse Events (AEs)
An AE is any untoward medical occurrence in a participant or in a clinical investigation participant administered a medicinal product and which does not necessarily have a causal relationship with this treatment. An unsolicited AE is an observed AE that does not fulfill the conditions pre-listed in the case report book (CRB) in terms of diagnosis and/or onset window post-vaccination. Systemic AEs are all AEs that were not injection or administration site reactions. Immediate events are recorded to capture medically relevant unsolicited systemic AEs (including those related to the product administered) that occur within the first 30 minutes after vaccination.
Measured: Cohorts 1 and 3: Within 30 minutes after vaccination on Day 0; Cohorts 2 and 4: Within 30 minutes after vaccination on Days 0 and 56
Number of Participants With Solicited Administration Site and Systemic Reactions
All noxious and unintended responses to a medicinal product related to any dose are considered adverse reactions (AR). A solicited reaction is an "expected" AR (sign or symptom) observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRB. An administration site reaction is an AR at and around the administration site. Systemic ARs are all ARs that are not injection or administration site reactions.
Measured: Cohorts 1 and 3: Within 28 days after vaccination on Day 0; Cohorts 2 and 4: Within 28 days after vaccination on Days 0 and 56
Number of Participants With Unsolicited Adverse Events
An AE is any untoward medical occurrence in a participant or in a clinical investigation participant administered a medicinal product and which does not necessarily have a causal relationship with this treatment. An unsolicited AE is an observed AE that does not fulfill the conditions pre-listed in the CRB in terms of diagnosis and/or onset window post-vaccination.
Measured: Cohorts 1 and 3: Within 28 days after vaccination on Day 0; Cohorts 2 and 4: Within 28 days after vaccination on Days 0 and 56
Number of Participants With Adverse Events of Special Interest (AESIs)
An AESI is one of scientific and medical concern specific to the Sponsor's product or program, for which ongoing monitoring and rapid communication by the investigator to the sponsor can be appropriate.
Measured: Cohorts 1 and 3: Within 28 days after vaccination on Day 0; Cohorts 2 and 4: Within 28 days after vaccination on Days 0 and 56
Number of Participants With Medically Attended Adverse Events (MAAEs)
An MAAE is a new onset or a worsening of a condition that prompts the participant or participant's parent/guardian/legally authorized representative to seek unplanned medical advice at a physician's office or Emergency Department.
Measured: Cohorts 1 and 3: Within 28 days after vaccination on Day 0; Cohorts 2 and 4: Within 28 days after vaccination on Days 0 and 56
Number of Participants With Serious Adverse Events (SAEs)
An SAE is any untoward medical occurrence that at any dose results in death or is life-threatening or requires inpatient hospitalization or prolongation of existing hospitalization or results in persistent or significant disability/incapacity or is a congenital anomaly/birth defect or is an important medical event.
Measured: From the first study vaccine administration (Day 0) up to end of the study, maximum of 12 months
Geometric Mean Titers Against RSV A Neutralizing Antibody in RSV-Naïve Participants
RSV A neutralizing antibody measured by microneutralization. RSV-naïve participants are defined as undetectable serum anti-RSV A IgA antibodies.
Measured: Cohorts 1 and 3: Day 56; Cohorts 2 and 4: Days 56 and 84
Secondary outcomes (6)
Titer of Vaccine Virus Shedding Measured by Reverse Transcription Polymerase Chain Reaction (RT-PCR)
Shedding of the attenuated RSV vaccine strain in nasal swab samples was evaluated by RSV quantitative RT-PCR (qRT-PCR) assay, which specifically detected and quantified RSVt ΔNS2 vaccine strain (RSV ΔNS2/Δ1313/I1314L) in human nasal swab samples.
Measured: Cohorts 1 and 3: Day 7; Cohorts 2 and 4: Days 7 and 63
Percentage of Participants Infected With Vaccine Virus at Days 56 and 84
Infection is defined as detection of vaccine virus in nasal swab by RT-PCR and/or a >= 4-fold rise in RSV A serum neutralizing antibody titers, or in RSV serum anti-F immunoglobulin G (IgG) antibody titers.
Measured: Cohorts 1 and 3: Day 56; Cohorts 2 and 4: Days 56 and 84
Geometric Mean Titers Against RSV A Neutralizing Antibody in RSV-Experienced Participants
RSV A neutralizing antibody measured by microneutralization. RSV-experienced participants are defined as detectable serum anti-RSV A IgA antibodies. CI= confidence interval.
Measured: Cohorts 1 and 3: Day 56; Cohorts 2 and 4: Days 56 and 84
Geometric Mean Titers Against Serum Anti-F Immunoglobulin G (IgG) Antibody
The IgG antibodies to RSV F antigen was measured using the anti RSV F IgG ELISA. RSV-naïve and RSV-experienced participants are defined as undetectable or detectable serum anti-RSV A IgA antibodies, respectively.
Measured: Cohorts 1 and 3: Day 56; Cohorts 2 and 4: Days 56 and 84
Geometric Mean Titers Against RSV A Neutralizing Antibody After the RSV Surveillance Season
RSV A neutralizing antibody measured by microneutralization. RSV-naïve and RSV-experienced participants are defined as undetectable or detectable serum anti-RSV A IgA antibodies, respectively.
Measured: Cohorts 1 and 3: Within 5 months after vaccination on Day 0; Cohorts 2 and 4: Within 5 months after vaccination on Day 56
Geometric Mean Titers Against Serum Anti-F Immunoglobulin G Antibody After the RSV Surveillance Season
The IgG antibodies to RSV F antigen was measured using the anti RSV F IgG ELISA. RSV-naïve and RSV-experienced participants are defined as undetectable or detectable serum anti-RSV A IgA antibodies, respectively.
Measured: Cohorts 1 and 3: Within 5 months after vaccination on Day 0; Cohorts 2 and 4: Within 5 months after vaccination on Day 56
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted29 Jul 2020
- Study start17 Sep 2020
- Primary completion13 Apr 2023
- Study completion13 Apr 2023
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Publications (2)Papers the sponsor has linked to this study.
- Other trials for Respiratory Syncytial Virus InfectionStudies of the same condition, open and under way.
- More trials run by Sanofi Pasteur, a Sanofi CompanyThe 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 1/2
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Sequential
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 259 participants (actual)
Sponsor and investigators
- Lead sponsor
- Sanofi Pasteur, a Sanofi Company
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Clinical Sciences & Operations, Study director, Sanofi Pasteur, a Sanofi Company
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04491877
- Sponsor's protocol ID
- VAD00001
- Other IDs
- U1111-1238-1869
- Acronym
- VAD00001
- Status last verified
- Sep 2025
- First submitted
- 27 Jul 2020
- Last updated
- 9 Sep 2025
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- No
- 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
Publications
Idoko OT, Vargas SL, Bueso A, Rivera D, Edward H, Banooni P, Berger S, Janicot S, Vercasson C, Pallardy S, Nteene R, Adhikarla H, Gerchman E, Gasparotto M, Gallichan S, Rivas E, Buchholz UJ, Sesay S, Gurunathan S, De Bruijn I, Dhingra MS. Immunogenicity and shedding of live-attenuated intranasal respiratory syncytial virus vaccine in children aged 6-18 months by baseline serostatus: a multicentre, randomised, placebo-controlled, phase 1/2 trial. Lancet Microbe. 2026 Oct 13:101447. doi: 10.1016/j.lanmic.2026.101447. Online ahead of print.
PubMed 42869044Idoko OT, Vargas SL, Bueso A, Rivera D, Edward H, Simon M, Banooni P, Berger S, Janicot S, Vercasson C, Pallardy S, Nteene R, Adhikarla H, Gerchman E, Gasparotto M, Gallichan S, Rivas E, Buchholz UJ, Collins PL, Sesay S, Gurunathan S, De Bruijn I, Dhingra MS. Live-Attenuated Intranasal RSV Vaccine in Infants and Toddlers. NEJM Evid. 2025 Sep;4(9):EVIDoa2500026. doi: 10.1056/EVIDoa2500026. Epub 2025 Aug 26.
PubMed 40856556
Study at a glance
From the registry record, last updated by the sponsor on 9 Sep 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Safety, Immunogenicity, Infectivity, and Dose-Finding Study of an Investigational Live-Attenuated Respiratory Syncytial Virus (RSV) Vaccine in Infants and Toddlers
- ClinicalTrials.gov ID
- NCT04491877
- Acronym / sponsor ID
- VAD00001 / VAD00001
- Conditions
- Respiratory Syncytial Virus Infection
- Phase
- Phase 1/2
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 259 participants (actual)
- Lead sponsor
- Sanofi Pasteur, a Sanofi CompanyIndustry (pharma, biotech, devices)
- Study start
- 17 Sep 2020 (actual)
- Primary completion
- 13 Apr 2023 (actual)
- Study completion
- 13 Apr 2023 (actual)
- First posted
- 29 Jul 2020 (actual)
- Results
- Posted 13 Jun 2024
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The primary objectives of the study were:
- To assess the safety profile of each dose of the study product after each and any administration in all infants and toddlers regardless of baseline serostatus.
- To characterize the Respiratory Syncytial Virus (RSV) A serum neutralizing antibody responses to the study product in each vaccine group after vaccination in RSV-naïve participants.
The secondary objectives of the study were:
- To quantify the amount of vaccine virus shed by each participant by baseline serostatus.
- To determine the proportion of vaccinated infants and toddlers in each vaccine group infected with the vaccine virus at D56 (56 days after vaccination 1) for Cohorts 1, 2, 3 and 4, and at Day 84 (28 days after vaccination 2) for Cohorts 2 and 4 by baseline serostatus.
- To characterize the RSV A serum neutralizing antibody responses to the study product in each vaccine group after vaccination in RSV-experienced participants.
- To characterize serum RSV anti-F immunoglobulin G (IgG) antibody responses to the study product in each vaccine group after vaccination by baseline serostatus.
- To characterize serum RSV antibody responses (RSV A-neutralizing and anti-RSV F IgG) to the study product in each vaccine group after the RSV surveillance season or at least 5 months after the last vaccine administration by baseline serostatus.
Detailed description
Study duration per participant was maximum 12 months
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Sequential
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 9
| Arm | Type | Receives |
|---|---|---|
| Cohort 1 (RSV vaccine formulation 1) | Experimental | Biological: RSV vaccine formulation 11 administration of RSV vaccine formulation 1 on Day 0 |
| Cohort 1 (Placebo) | Placebo comparator | Biological: Placebo1 administration of placebo on Day 0 |
| Cohort 2 (RSV vaccine formulation 1) | Experimental | Biological: RSV vaccine formulation 12 administrations of RSV vaccine formulation 1 on Day 0 and Day 56 |
| Cohort 2 (Placebo) | Placebo comparator | Biological: Placebo2 administrations of placebo on Day 0 and Day 56 |
| Cohort 3 (RSV vaccine formulation 2) | Experimental | Biological: RSV vaccine formulation 21 administration of RSV vaccine formulation 2 on Day 0 |
| Cohort 3 (Placebo) | Placebo comparator | Biological: Placebo1 administration of placebo on Day 0 |
| Cohort 4 (RSV vaccine formulation 1) | Experimental | Biological: RSV vaccine formulation 12 administrations of RSV vaccine formulation 1 on Day 0 and Day 56 |
| Cohort 4 (RSV vaccine formulation 2) | Experimental | Biological: RSV vaccine formulation 22 administrations of RSV vaccine formulation 2 on Day 0 and Day 56 |
| Cohort 4 (Placebo) | Placebo comparator | Biological: Placebo2 administrations of placebo on Day 0 and Day 56 |
Who may qualify
- Ages
- 6 to 18 months
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Child
Key inclusion criteria (3 listed)
- Aged 6 through 18 months at Day 0.
- Informed consent form has been signed and dated by the parent(s) or other legally acceptable representative (and by independent witness if required by local regulations).
- Participant and parent / guardian / legally acceptable representative are able to attend all scheduled visits and to comply with all trial procedures
Key exclusion criteria (42 listed)
- Born at less than 34 weeks gestation
- Born at less than 37 weeks gestation and less than 1 year of age at the time
- 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).
- Probable or confirmed case of Coronavirus Disease 2019 (COVID-19).
- Known systemic hypersensitivity to any of the vaccine components, or history of a life-threatening reaction to the vaccine used in the trial or to a vaccine containing any of the same substances
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 |
|---|---|---|
| RSV vaccine formulation 1Pharmaceutical form: Suspension of virus Route of administration: Intranasal | Biological | Cohort 1 (RSV vaccine formulation 1), Cohort 2 (RSV vaccine formulation 1), Cohort 4 (RSV vaccine formulation 1) |
| RSV vaccine formulation 2Pharmaceutical form: Suspension of virus Route of administration: Intranasal | Biological | Cohort 3 (RSV vaccine formulation 2), Cohort 4 (RSV vaccine formulation 2) |
| PlaceboPharmaceutical form: Suspension Route of administration: Intranasal | Biological | Cohort 1 (Placebo), Cohort 2 (Placebo), Cohort 3 (Placebo), Cohort 4 (Placebo) |
Primary outcome
Number of Participants With Immediate Unsolicited Systemic Adverse Events (AEs)
Time frame: Cohorts 1 and 3: Within 30 minutes after vaccination on Day 0; Cohorts 2 and 4: Within 30 minutes after vaccination on Days 0 and 56
An AE is any untoward medical occurrence in a participant or in a clinical investigation participant administered a medicinal product and which does not necessarily have a causal relationship with this treatment. An unsolicited AE is an observed AE that does not fulfill the conditions pre-listed in the case report book (CRB) in terms of diagnosis and/or onset window post-vaccination. Systemic AEs are all AEs that were not injection or administration site reactions. Immediate events are recorded to capture medically relevant unsolicited systemic AEs (including those related to the product administered) that occur within the first 30 minutes after vaccination.
Number of Participants With Solicited Administration Site and Systemic Reactions
Time frame: Cohorts 1 and 3: Within 28 days after vaccination on Day 0; Cohorts 2 and 4: Within 28 days after vaccination on Days 0 and 56
All noxious and unintended responses to a medicinal product related to any dose are considered adverse reactions (AR). A solicited reaction is an "expected" AR (sign or symptom) observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRB. An administration site reaction is an AR at and around the administration site. Systemic ARs are all ARs that are not injection or administration site reactions.
Number of Participants With Unsolicited Adverse Events
Time frame: Cohorts 1 and 3: Within 28 days after vaccination on Day 0; Cohorts 2 and 4: Within 28 days after vaccination on Days 0 and 56
An AE is any untoward medical occurrence in a participant or in a clinical investigation participant administered a medicinal product and which does not necessarily have a causal relationship with this treatment. An unsolicited AE is an observed AE that does not fulfill the conditions pre-listed in the CRB in terms of diagnosis and/or onset window post-vaccination.
Number of Participants With Adverse Events of Special Interest (AESIs)
Time frame: Cohorts 1 and 3: Within 28 days after vaccination on Day 0; Cohorts 2 and 4: Within 28 days after vaccination on Days 0 and 56
An AESI is one of scientific and medical concern specific to the Sponsor's product or program, for which ongoing monitoring and rapid communication by the investigator to the sponsor can be appropriate.
Number of Participants With Medically Attended Adverse Events (MAAEs)
Time frame: Cohorts 1 and 3: Within 28 days after vaccination on Day 0; Cohorts 2 and 4: Within 28 days after vaccination on Days 0 and 56
An MAAE is a new onset or a worsening of a condition that prompts the participant or participant's parent/guardian/legally authorized representative to seek unplanned medical advice at a physician's office or Emergency Department.
Number of Participants With Serious Adverse Events (SAEs)
Time frame: From the first study vaccine administration (Day 0) up to end of the study, maximum of 12 months
An SAE is any untoward medical occurrence that at any dose results in death or is life-threatening or requires inpatient hospitalization or prolongation of existing hospitalization or results in persistent or significant disability/incapacity or is a congenital anomaly/birth defect or is an important medical event.
Geometric Mean Titers Against RSV A Neutralizing Antibody in RSV-Naïve Participants
Time frame: Cohorts 1 and 3: Day 56; Cohorts 2 and 4: Days 56 and 84
RSV A neutralizing antibody measured by microneutralization. RSV-naïve participants are defined as undetectable serum anti-RSV A IgA antibodies.
6 secondary outcomes
Titer of Vaccine Virus Shedding Measured by Reverse Transcription Polymerase Chain Reaction (RT-PCR)
Time frame: Cohorts 1 and 3: Day 7; Cohorts 2 and 4: Days 7 and 63
Percentage of Participants Infected With Vaccine Virus at Days 56 and 84
Time frame: Cohorts 1 and 3: Day 56; Cohorts 2 and 4: Days 56 and 84
Geometric Mean Titers Against RSV A Neutralizing Antibody in RSV-Experienced Participants
Time frame: Cohorts 1 and 3: Day 56; Cohorts 2 and 4: Days 56 and 84
Geometric Mean Titers Against Serum Anti-F Immunoglobulin G (IgG) Antibody
Time frame: Cohorts 1 and 3: Day 56; Cohorts 2 and 4: Days 56 and 84
Geometric Mean Titers Against RSV A Neutralizing Antibody After the RSV Surveillance Season
Time frame: Cohorts 1 and 3: Within 5 months after vaccination on Day 0; Cohorts 2 and 4: Within 5 months after vaccination on Day 56
Geometric Mean Titers Against Serum Anti-F Immunoglobulin G Antibody After the RSV Surveillance Season
Time frame: Cohorts 1 and 3: Within 5 months after vaccination on Day 0; Cohorts 2 and 4: Within 5 months after vaccination on Day 56
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 9 Sep 2025.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- Derived from this study: PubMed 42869044Idoko OT, Vargas SL, Bueso A, Rivera D, Edward H, Banooni P, Berger S, Janicot S, Vercasson C, Pallardy S, Nteene R, Adhikarla H, Gerchman E, Gasparotto M, Gallichan S, Rivas E, Buchholz UJ, Sesay S, Gurunathan S, De Bruijn I, Dhingra MS. Immunogenicity and shedding of live-attenuated intranasal respiratory syncytial virus vaccine in children aged 6-18 months by baseline serostatus: a multicentre, randomised, placebo-controlled, phase 1/2 trial. Lancet Microbe. 2026 Oct 13:101447. doi: 10.1016/j.lanmic.2026.101447. Online ahead of print.
- Derived from this study: PubMed 40856556Idoko OT, Vargas SL, Bueso A, Rivera D, Edward H, Simon M, Banooni P, Berger S, Janicot S, Vercasson C, Pallardy S, Nteene R, Adhikarla H, Gerchman E, Gasparotto M, Gallichan S, Rivas E, Buchholz UJ, Collins PL, Sesay S, Gurunathan S, De Bruijn I, Dhingra MS. Live-Attenuated Intranasal RSV Vaccine in Infants and Toddlers. NEJM Evid. 2025 Sep;4(9):EVIDoa2500026. doi: 10.1056/EVIDoa2500026. Epub 2025 Aug 26.
- VAD00001 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. This study is not recruiting at the moment.
Clinical Sciences & Operations study director
Sanofi Pasteur, a Sanofi Company
29 sites in 3 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1/2 study testing RSV vaccine formulation 1 and RSV vaccine formulation 2 in people with Respiratory Syncytial Virus Infection, run by Sanofi Pasteur, a Sanofi Company at 29 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 3 inclusion and 42 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: finished, as of the sponsor's last update on 9 Sep 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 29 sites in United States, Chile, Honduras. 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. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this combined phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
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 13 Jun 2024). 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?
Number of Participants With Immediate Unsolicited Systemic Adverse Events (AEs) (time frame: Cohorts 1 and 3: Within 30 minutes after vaccination on Day 0; Cohorts 2 and 4: Within 30 minutes after vaccination on Days 0 and 56). The study lists 7 primary outcomes in all. 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 NCT04491877, which also lists 2 linked publications.
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 9 Sep 2025.