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TerminatedNCT06705140OPALUpdated Aug 3, 2026Results posted

A Study on the Immunogenicity and Safety of 3 Different Dose Concentrations of a Respiratory Syncytial Virus Vaccine in Infants and Toddlers

A Phase 3 interventional study of Low Dose (LD) RSVt vaccine and Standard Dose (SD) RSVt vaccine in RSV Immunisation and Healthy Volunteers, sponsored by Sanofi Pasteur, a Sanofi Company. Terminated at 3 sites in Honduras. Open to participants aged 6 Months to 21 Months, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-08-03.

Sponsored by Sanofi Pasteur, a Sanofi Company · Phase 3, Interventional, and Prevention

Why this study was terminated
Sponsor decision
Phase
Phase 3
Study type
Interventional
Enrollment
42
Allocation
Randomized
Ages
6 Months to 21 Months
Sex
All
01

Study summary

This study was a Phase III, parallel group, randomized, observer blind, placebo controlled, multi-national, multi-center, multi-arm study conducted in 42 healthy children enrolled at 6 months to \<22 months of age. The purpose of the study was to evaluate the non-inferiority of the immune response of the lower dose (LD) when compared to the standard dose (SD) respiratory syncytial virus infant and toddler (RSVt) vaccine and the safety of the LD, SD and high dose (HD) vaccine in preterm born children and of the HD vaccine in full term born children administered by intranasal route and compared to placebo.

Read the detailed description

The study duration was approximately 8 months for each participant, including the 6 months safety follow-up phone call after the second study intervention administration.

02

Conditions studied

  • RSV Immunisation
  • Healthy Volunteers

Keywords

  • RSV
  • RSVt (RSV toddler and Infant) Vaccine
03

Who can participate

Ages eligible
6 Months to 21 Months
Sexes eligible
All
Accepts healthy volunteers
Yes

Inclusion criteria

  • Aged 6 months to \< 22 months on the day of inclusion (means from the day of the 6-month birthday to the day before the 22-month birthday. The second vaccine administration was administered before the study participant has turned 24 months of age).
  • Participants who were healthy as determined by medical evaluation including medical history.
  • For Cohort 1 and Cohort 2 (contingent upon satisfactory safety profile of the RSVt vaccine in Cohort 1):

    --Participant born 28 through 36 weeks of gestation 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.

  • For Cohort 2:

    • Participant born at full term of pregnancy (≥ 37 weeks of gestation).

Exclusion criteria

Exclusion Criteria:

Participants were 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 or radiation therapy, within the preceding 6 months; or long-term systemic corticosteroid therapy (prednisone or equivalent for more than 2 consecutive weeks within the past 3 months).
  • Known systemic hypersensitivity to any of the study intervention components, or history of a life-threatening reaction to the study intervention used in the study or to a product containing any of the same substances.

Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with study conduct or completion.

  • History of medically diagnosed wheezing. Children with a history of recurrent wheezing will be excluded. Children with a previous single episode of wheezing may be included if that episode of wheezing was not associated with hospitalization or if does not have a family history of wheezing.
  • Any acute febrile illness in the past 48 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.
  • Probable or confirmed ongoing case of viral respiratory infection (including COVID-19, influenza, rhinovirus, etc.) at the time of enrollment. A prospective participant should not be included in the study until the respiratory infection has resolved.
  • 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 study enrollment
    • a person who has received (within the past 6 months) or is receiving (at the time of enrollment) immunosuppressant agents
    • a person living with a solid organ or bone marrow transplant
  • Potential close contact with other immunocompromised individual within 30 days after each vaccination as per investigator's discretion.
  • Participant's biological mother's previous receipt or planned administration of an investigational RSV vaccine during pregnancy and/or breastfeeding.
  • Receipt or planned receipt of any of the following vaccines prior to enrollment or after the first study intervention administration:

    • Any other intranasal live attenuated vaccine within the 28 days prior to and after Dose 1 study administration
    • Unless given on the day of the first study intervention administration, any other injectable live attenuated vaccines within the 28 days prior to and after. Concomitant receipt on the day of the first study intervention administration is allowed
  • Planned receipt of any monoclonal antibody for RSV (such as Nirsevimab or Palivizumab) for the duration of the study.
  • Previous receipt of an investigational RSV vaccine or receiving any anti-RSV product (such as ribavirin or RSV immune globulin) at the time of enrollment. Previous receipt of an RSV monoclonal antibody within 6 months prior to the first study vaccine administration.
  • Receipt of immune globulins, blood or blood-derived products in the past 3 months
  • Receipt of intranasal and intra-ocular medications within 3 days prior to study enrollment
  • Participation at the time of study enrollment or planned participation during the present study period in another clinical study investigating a vaccine, drug, medical device, or medical procedure

Note: The above information is not intended to contain all considerations relevant to a potential participation in a clinical trial.

04

Study design

Phase
Phase 3
Primary purpose
Prevention
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Triple (Participant, Investigator, Outcomes assessor)
Enrollment
42 participants (actual)

Study arms

  • Experimental
    Cohort 1: Group 1- (SD RSVt vaccine)

    Participants received 2 intranasal administrations of SD RSVt vaccine

    Biological: Standard Dose (SD) RSVt vaccine

  • Placebo comparator
    Cohort 1: Group 2-Control

    Participants received 2 intranasal administrations of placebo

    Biological: Placebo

  • Experimental
    Cohort 1: Group 3- (HD RSVt vaccine)

    Participants received 2 intranasal administrations of HD RSVt vaccine

    Biological: High Dose (HD) RSVt vaccine

  • Placebo comparator
    Cohort 1: Group 4-Control

    Participants received 2 intranasal administrations of placebo

    Biological: Placebo

  • Experimental
    Cohort 2: Group 1- (LD RSVt vaccine)

    Participants received 2 intranasal administrations of LD RSVt vaccine

    Biological: Low Dose (LD) RSVt vaccine

  • Experimental
    Cohort 2: Group 2- (SD RSVt vaccine)

    Participants received 2 intranasal administrations of SD RSVt vaccine

    Biological: Standard Dose (SD) RSVt vaccine

  • Experimental
    Cohort 2: Group 3- (HD RSVt vaccine

    Participants received 2 intranasal administrations of HD RSVt vaccine

    Biological: High Dose (HD) RSVt vaccine

  • Placebo comparator
    Cohort 2: Group 4-Control

    Participants received 2 intranasal administrations of placebo

    Biological: Placebo

Interventions

  • BiologicalLow Dose (LD) RSVt vaccine

    Pharmaceutical form: Liquid for nasal spray Route of administration: Intranasal

    Also known as: 534

  • BiologicalStandard Dose (SD) RSVt vaccine

    Pharmaceutical form:Liquid for nasal spray-Route of administration:Intranasal

    Also known as: 534

  • BiologicalHigh Dose (HD) RSVt vaccine

    Pharmaceutical form:Liquid for nasal spray-Route of administration:Intranasal

    Also known as: 534

  • BiologicalPlacebo

    Pharmaceutical form:Liquid for nasal spray-Route of administration:Intranasal

05

What researchers measure

Primary outcomes

  1. Cohort 2: Geometric Mean Titers (GMT) of RSV A Serum Neutralizing Antibodies at Day 85 (Post-Dose 2)

    Serum samples were planned to be collected at specified timepoints for immunogenicity assessments. RSV A serum neutralizing antibody titers were planned to be determined using a validated plaque reduction neutralization test (PRNT).

    Time frame: Day 85 (28 days post-vaccination 2)

  2. Cohort 2: Geometric Mean Titers of RSV B Serum Neutralizing Antibodies at Day 85 (Post-Dose 2)

    Serum samples were planned to be collected at specified timepoints for immunogenicity assessments. RSV B serum neutralizing antibody titers were planned to be determined using a validated PRNT.

    Time frame: Day 85 (28 days post-vaccination 2)

  3. Cohorts 1 and 2: Number of Participants With Immediate Unsolicited Systemic Adverse Events (AEs)

    An AE was any untoward medical occurrence in a clinical study participant temporally associated with the use of study vaccine, whether or not considered related to the study vaccine. An unsolicited AE was an observed AE that did not fulfill the conditions of solicited reactions, i.e., pre-listed in the case report form (CRF) in terms of diagnosis and onset window post-vaccination. All participants were observed for 30 minutes after each vaccination and any unsolicited AEs that occurred during that time were recorded as immediate unsolicited AEs.

    Time frame: Up to 30 minutes after each vaccination (post-dose on Day 1)

  4. Cohorts 1 and 2: Number of Participants With Solicited Administration Site Reactions

    A solicited injection/administration site reactions were adverse reactions (AR) at and around the injection/administration site of the study vaccine observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRF and considered as related to the study vaccine administered.

    Time frame: Up to 21 days after each vaccination (post-dose on Day 1)

  5. Cohorts 1 and 2: 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 and considered as related to the study vaccine administered.

    Time frame: Up to 21 days after each vaccination (post-dose on Day 1)

  6. Cohorts 1 and 2: Number of Participants With Unsolicited Adverse Events

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

    Time frame: Up to 28 days after each vaccination (post-dose on Day 1)

  7. Cohorts 1 and 2: Number of Participants With Medically Attended Adverse Events (MAAEs)

    An MAAE was defined as a new onset or a worsening of a condition that prompted the participant or participant's parent/legally acceptable representative to seek unplanned medical advice at a physician's office or emergency department.

    Time frame: From first dose of study vaccine administration (Day 1) to 198 days

  8. Cohorts 1 and 2: Number of Participants With Serious Adverse Events (SAEs)

    An SAE was defined as 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 other medically important event.

    Time frame: From first dose of study vaccine administration (Day 1) to 198 days

  9. Cohorts 1 and 2: Number of Participants With Adverse Events of Special Interest (AESIs)

    An AESI (serious or non-serious) was one of scientific and medical concern specific to the sponsor's study vaccine or program, for which ongoing monitoring and rapid communication by the investigator to the sponsor was appropriate. Acute wheeze and anaphylaxis were collected as AESI.

    Time frame: From first dose of study vaccine administration (Day 1) to 198 days

Secondary outcomes

  1. Cohort 1: Geometric Mean Titers of RSV A and B Serum Neutralizing Antibodies at Baseline (Day 1) and Day 85

    Serum samples were planned to be collected at specified timepoints for immunogenicity assessments. RSV A and RSV B serum neutralizing antibody titers were planned to be determined using a validated PRNT.

    Time frame: Baseline (Day 1) and Day 85

  2. Cohorts 1 and 2: Mean Titers of RSV Serum Anti-F Immunoglobulin (Ig) A and IgG Antibodies at Baseline (Day 1) and Day 85

    Serum samples were collected at specified timepoints for immunogenicity assessments. Antibodies to RSV F antigen were measured using the anti-RSV serum anti-F IgA and IgG using electrochemiluminescence method. Log10 titer values are reported.

    Time frame: Baseline (Day 1) and Day 85

  3. Cohorts 1 and 2: Percentage of Participants With Quantified Shedding >=3.37 Lower Limit of Quantitation (LLOQ)

    Nasal swabs were collected to assess shedding of the attenuated RSV vaccine strain at specified timepoints. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay was developed to detect and quantify RSV ΔNS2 candidate in nasal swab samples. Percentages rounded off to tenth decimal place.

    Time frame: Day 8 and Day 64

  4. Cohorts 1 and 2: Percentage of Participants With Detectable Shedding >=2.08 Limit of Detection

    Nasal swabs were collected to assess shedding of the attenuated RSV vaccine strain at specified timepoints. qRT-PCR assay was developed to detect and quantify RSV ΔNS2 candidate in nasal swab samples. Percentages rounded off to tenth decimal place.

    Time frame: Day 8 and Day 64

  5. Cohorts 1 and 2: Titer of Vaccine Virus Shedding in Participants Detected in Nasal Samples Quantified by Quantitative Real Time-Polymerase Chain Reaction

    Nasal swabs were collected to assess shedding of the attenuated RSV vaccine strain at specified timepoints. qRT-PCR assay was developed to detect and quantify RSV ΔNS2 candidate in nasal swab samples. Quantified virus shedding was defined as vaccine virus shedding \>=lower limit of quantification (LLOQ=3.37 log10 copies/mL).

    Time frame: Day 8 and Day 64

06

Results

Posted Aug 3, 2026
Limitations and caveats
The study was terminated early as per sponsor's decision (no safety concerns).

Participant flow

Study was conducted at 1 center in a single country from 25 November 2024 to 13 December 2024. 42 healthy infants/toddlers aged 6 to\<22 months were randomized to 2 cohorts: preterm born children(Cohort1:randomized to receive either placebo or standard dose of live-attenuated respiratory syncytial virus delta\[Δ\] non-structural \[NS\]2/Δ1313/I1314L vaccine \[RSVt vaccine\]) and full term born children (Cohort2:randomized to receive either low dose, standard dose or high dose RSVt vaccine or placebo).

Participant flow — Overall Study
MilestoneCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Started231010125
Completed231010125
Not completed000000

Outcome measures

PrimaryCohort 2: Geometric Mean Titers (GMT) of RSV A Serum Neutralizing Antibodies at Day 85 (Post-Dose 2)

Serum samples were planned to be collected at specified timepoints for immunogenicity assessments. RSV A serum neutralizing antibody titers were planned to be determined using a validated plaque reduction neutralization test (PRNT).

Time frame:
Day 85 (28 days post-vaccination 2)

No measurements were reported for this outcome.

PrimaryCohort 2: Geometric Mean Titers of RSV B Serum Neutralizing Antibodies at Day 85 (Post-Dose 2)

Serum samples were planned to be collected at specified timepoints for immunogenicity assessments. RSV B serum neutralizing antibody titers were planned to be determined using a validated PRNT.

Time frame:
Day 85 (28 days post-vaccination 2)

No measurements were reported for this outcome.

PrimaryCohorts 1 and 2: Number of Participants With Immediate Unsolicited Systemic Adverse Events (AEs)

An AE was any untoward medical occurrence in a clinical study participant temporally associated with the use of study vaccine, whether or not considered related to the study vaccine. An unsolicited AE was an observed AE that did not fulfill the conditions of solicited reactions, i.e., pre-listed in the case report form (CRF) in terms of diagnosis and onset window post-vaccination. All participants were observed for 30 minutes after each vaccination and any unsolicited AEs that occurred during that time were recorded as immediate unsolicited AEs.

Time frame:
Up to 30 minutes after each vaccination (post-dose on Day 1)
Reported as:
Count of participants · Participants
Cohorts 1 and 2: Number of Participants With Immediate Unsolicited Systemic Adverse Events (AEs)
ParticipantsCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Cohorts 1 and 2: Number of Participants With Immediate Unsolicited Systemic Adverse Events (AEs)000000
PrimaryCohorts 1 and 2: Number of Participants With Solicited Administration Site Reactions

A solicited injection/administration site reactions were adverse reactions (AR) at and around the injection/administration site of the study vaccine observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRF and considered as related to the study vaccine administered.

Time frame:
Up to 21 days after each vaccination (post-dose on Day 1)
Reported as:
Count of participants · Participants
Cohorts 1 and 2: Number of Participants With Solicited Administration Site Reactions
ParticipantsCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Cohorts 1 and 2: Number of Participants With Solicited Administration Site Reactions026843
PrimaryCohorts 1 and 2: 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 and considered as related to the study vaccine administered.

Time frame:
Up to 21 days after each vaccination (post-dose on Day 1)
Reported as:
Count of participants · Participants
Cohorts 1 and 2: Number of Participants With Solicited Systemic Reactions
ParticipantsCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Cohorts 1 and 2: Number of Participants With Solicited Systemic Reactions024664
PrimaryCohorts 1 and 2: Number of Participants With Unsolicited Adverse Events

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

Time frame:
Up to 28 days after each vaccination (post-dose on Day 1)
Reported as:
Count of participants · Participants
Cohorts 1 and 2: Number of Participants With Unsolicited Adverse Events
ParticipantsCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Cohorts 1 and 2: Number of Participants With Unsolicited Adverse Events000100
PrimaryCohorts 1 and 2: Number of Participants With Medically Attended Adverse Events (MAAEs)

An MAAE was defined as a new onset or a worsening of a condition that prompted the participant or participant's parent/legally acceptable representative to seek unplanned medical advice at a physician's office or emergency department.

Time frame:
From first dose of study vaccine administration (Day 1) to 198 days
Reported as:
Count of participants · Participants
Cohorts 1 and 2: Number of Participants With Medically Attended Adverse Events (MAAEs)
ParticipantsCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Cohorts 1 and 2: Number of Participants With Medically Attended Adverse Events (MAAEs)112020
PrimaryCohorts 1 and 2: Number of Participants With Serious Adverse Events (SAEs)

An SAE was defined as 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 other medically important event.

Time frame:
From first dose of study vaccine administration (Day 1) to 198 days
Reported as:
Count of participants · Participants
Cohorts 1 and 2: Number of Participants With Serious Adverse Events (SAEs)
ParticipantsCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Cohorts 1 and 2: Number of Participants With Serious Adverse Events (SAEs)010000
PrimaryCohorts 1 and 2: Number of Participants With Adverse Events of Special Interest (AESIs)

An AESI (serious or non-serious) was one of scientific and medical concern specific to the sponsor's study vaccine or program, for which ongoing monitoring and rapid communication by the investigator to the sponsor was appropriate. Acute wheeze and anaphylaxis were collected as AESI.

Time frame:
From first dose of study vaccine administration (Day 1) to 198 days
Reported as:
Count of participants · Participants
Cohorts 1 and 2: Number of Participants With Adverse Events of Special Interest (AESIs)
ParticipantsCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Cohorts 1 and 2: Number of Participants With Adverse Events of Special Interest (AESIs)000000
SecondaryCohort 1: Geometric Mean Titers of RSV A and B Serum Neutralizing Antibodies at Baseline (Day 1) and Day 85

Serum samples were planned to be collected at specified timepoints for immunogenicity assessments. RSV A and RSV B serum neutralizing antibody titers were planned to be determined using a validated PRNT.

Time frame:
Baseline (Day 1) and Day 85

No measurements were reported for this outcome.

SecondaryCohorts 1 and 2: Mean Titers of RSV Serum Anti-F Immunoglobulin (Ig) A and IgG Antibodies at Baseline (Day 1) and Day 85

Serum samples were collected at specified timepoints for immunogenicity assessments. Antibodies to RSV F antigen were measured using the anti-RSV serum anti-F IgA and IgG using electrochemiluminescence method. Log10 titer values are reported.

Time frame:
Baseline (Day 1) and Day 85
Reported as:
Mean · titer
Cohorts 1 and 2: Mean Titers of RSV Serum Anti-F Immunoglobulin (Ig) A and IgG Antibodies at Baseline (Day 1) and Day 85
titerCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Baseline (Day 1): IgA1.20 ± 0.6221.45 ± 1.521.35 ± 0.8810.502 ± 0.3641.56 ± 0.9530.921 ± 0.863
Baseline (Day 1): IgG0.709 ± 1.141.79 ± 1.872.55 ± 0.8780.935 ± 0.7982.55 ± 0.9111.57 ± 1.22
SecondaryCohorts 1 and 2: Percentage of Participants With Quantified Shedding >=3.37 Lower Limit of Quantitation (LLOQ)

Nasal swabs were collected to assess shedding of the attenuated RSV vaccine strain at specified timepoints. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay was developed to detect and quantify RSV ΔNS2 candidate in nasal swab samples. Percentages rounded off to tenth decimal place.

Time frame:
Day 8 and Day 64
Reported as:
Number · percentage of participants
Cohorts 1 and 2: Percentage of Participants With Quantified Shedding >=3.37 Lower Limit of Quantitation (LLOQ)
percentage of participantsCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Day 80 (0 to 84.2)0 (0 to 70.8)0 (0 to 30.8)40.0 (12.2 to 73.8)25.0 (5.5 to 57.2)0 (0 to 52.2)
SecondaryCohorts 1 and 2: Percentage of Participants With Detectable Shedding >=2.08 Limit of Detection

Nasal swabs were collected to assess shedding of the attenuated RSV vaccine strain at specified timepoints. qRT-PCR assay was developed to detect and quantify RSV ΔNS2 candidate in nasal swab samples. Percentages rounded off to tenth decimal place.

Time frame:
Day 8 and Day 64
Reported as:
Number · percentage of participants
Cohorts 1 and 2: Percentage of Participants With Detectable Shedding >=2.08 Limit of Detection
percentage of participantsCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Day 80 (0 to 84.2)0 (0 to 70.8)0 (0 to 30.8)50.0 (18.7 to 81.3)33.3 (9.9 to 65.1)0 (0 to 52.2)
SecondaryCohorts 1 and 2: Titer of Vaccine Virus Shedding in Participants Detected in Nasal Samples Quantified by Quantitative Real Time-Polymerase Chain Reaction

Nasal swabs were collected to assess shedding of the attenuated RSV vaccine strain at specified timepoints. qRT-PCR assay was developed to detect and quantify RSV ΔNS2 candidate in nasal swab samples. Quantified virus shedding was defined as vaccine virus shedding \>=lower limit of quantification (LLOQ=3.37 log10 copies/mL).

Time frame:
Day 8 and Day 64
Reported as:
Mean · log10 copies/mL
Cohorts 1 and 2: Titer of Vaccine Virus Shedding in Participants Detected in Nasal Samples Quantified by Quantitative Real Time-Polymerase Chain Reaction
log10 copies/mLCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
Day 8———5.20 ± 1.024.91 ± 1.33—

Adverse events

Collected over Adverse events and death were collected from first dose of study vaccine administration (Day 1) up to end of follow-up per participant, 198 days.. Non-serious events are listed at a 5% frequency threshold.

Adverse event summary by group
GroupDeathsSeriousOther
Cohort 1: Group 1: Standard Dose RSVt0/2 (0%)0/2 (0%)0/2 (0%)
Cohort 1: Group 2: Placebo0/3 (0%)1/3 (33.3%)3/3 (100%)
Cohort 2: Group 1: Low Dose RSVt0/10 (0%)0/10 (0%)6/10 (60%)
Cohort 2: Group 2: Standard Dose RSVt0/10 (0%)0/10 (0%)9/10 (90%)
Cohort 2: Group 3: High Dose RSVt0/12 (0%)0/12 (0%)7/12 (58.3%)
Cohort 2: Group 4: Placebo0/5 (0%)0/5 (0%)4/5 (80%)
Most frequent serious events
Most frequent serious events
EventCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
PneumoniaInfections and infestations0/21/30/100/100/120/5
Most frequent other events
Most frequent other events
EventCohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: Placebo
RhinorrhoeaRespiratory, thoracic and mediastinal disorders0/22/36/108/104/122/5
Nasal CongestionRespiratory, thoracic and mediastinal disorders0/21/33/107/101/123/5
Decreased AppetiteMetabolism and nutrition disorders0/20/32/105/102/123/5
CryingGeneral disorders0/20/32/104/103/121/5
SomnolenceNervous system disorders0/21/31/102/102/121/5
VomitingGastrointestinal disorders0/21/32/103/102/121/5
IrritabilityPsychiatric disorders0/20/31/103/102/121/5
PyrexiaGeneral disorders0/20/30/101/102/120/5
NasopharyngitisInfections and infestations0/20/30/101/100/120/5

Baseline characteristics

Randomized analysis set consisted of participants for whom a study vaccine group had been allocated.

Age, Continuous
Age, Continuous(months)Cohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: PlaceboTotal
Mean16.5 ± 0.70714.0 ± 5.2013.0 ± 3.7110.9 ± 2.6911.8 ± 3.3810.0 ± 2.1212.0 ± 3.43
Sex: Female, Male
Sex: Female, Male(Participants)Cohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: PlaceboTotal
Female11347117
Male12765425
Race (NIH/OMB)
Race (NIH/OMB)(Participants)Cohort 1: Group 1: Standard Dose RSVtCohort 1: Group 2: PlaceboCohort 2: Group 1: Low Dose RSVtCohort 2: Group 2: Standard Dose RSVtCohort 2: Group 3: High Dose RSVtCohort 2: Group 4: PlaceboTotal
American Indian or Alaska Native0000000
Asian0000000
Native Hawaiian or Other Pacific Islander0000000
Black or African American23101012542
White0000000
More than one race0000000
Unknown or Not Reported0000000
07

Study locations

3 sites
  • Investigational Site Number : 3400002
    San Pedro Sula, Honduras
  • Investigational Site Number : 3400001
    Tegucigalpa, 11101, Honduras
  • Investigational Site Number : 3400003
    Tegucigalpa, 11101, Honduras
08

References and documents

Study documents

  • Study protocol · Sep 24, 2025
  • Statistical analysis plan · Feb 9, 2026

Documents are hosted by the registry — open the source record to download them.

Individual participant data

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

09

Registry details

Key details

Study ID
NCT06705140
Lead sponsor
Sanofi Pasteur, a Sanofi Company
Responsible party
Sponsor
First posted
Nov 26, 2024
Start date
Nov 25, 2024
Primary completion
Jun 11, 2025
Completion
Jun 11, 2025
Results posted
Aug 3, 2026
Last update
Aug 3, 2026

Oversight

Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

Not currently enrolling

This study is terminated, as verified in Jul 2026. You cannot join it, but the record below documents what was studied.

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Discussion

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