Study on a Live-attenuated Respiratory Syncytial Virus Vaccine for Assessment of Safety, Transmissibility, and Genetic Stability of the Vaccine Virus Among Close Contacts in Infants and Toddlers 6 to < 24 Months of Age in Puerto Rico (USA)

Phase II, Randomized, Observer-blind, Placebo-controlled, Multi-center Study of a Live Attenuated Respiratory Syncytial Virus Vaccine to Assess the Vaccine Virus' Transmissibility in Household or Daycare Center Settings, Shedding, and Genetic Stability, and to Describe the Immunogenicity and Safety of the Vaccine in Infants and Toddlers 6 to < 24 Months of Age in Puerto Rico (USA)

The primary purpose of the study is to assess the shedding, transmission, and genetic stability of the live-attenuated RSVt vaccine after each intranasal vaccination (56 days apart) in infants and toddlers 6 to < 24 months of age.

Study Overview

• Status: Completed
• Conditions: Respiratory Syncytial Virus Infection
• Intervention / Treatment: Biological: RSVt Vaccine; Other: Control Group

Detailed Description

The duration of each participant's participation is up to 8 months, including the 6 months safety follow-up phone call after the second study intervention administration for the pediatric participants The treatment administration for the pediatric participants will be on D01 and D57 (1 intranasal administration each).

• Study Type: Interventional
• Enrollment (Actual): 80
• Phase: Phase 2; Phase 1

Contacts and Locations

Study Locations

• Puerto Rico
  • Bayamón, Puerto Rico, 00960
    • Investigational Site Number : 6300004
  • Carolina, Puerto Rico, 984
    • Investigational Site Number : 6300002
  • Guayama, Puerto Rico, 00784
    • Investigational Site Number : 6300003
  • San Juan, Puerto Rico, 00918
    • Investigational Site Number : 6300001
• United States
  • Nebraska
    • Norfolk, Nebraska, United States, 68701
      • Meridian Clinical Research Norfolk Site Number : 8400003
    • Omaha, Nebraska, United States, 68134
      • Velocity Clinical Research, Omaha Site Number : 8400001

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 6 months to 1 year (Child)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Aged 6 months to < 24 months on the day of inclusion (from the day of the 6 months after birth to the day before the 2nd birthday)
• Participants who are healthy as determined by medical evaluation including medical history.
• Born at full term of pregnancy (≥ 37 weeks) or born after a gestation period of 27 through 36 weeks and medically stable as assessed by the investigator, based on the following definition: "Medically stable" refers to the condition of premature infants who do not require significant medical support or ongoing management for debilitating disease and who have demonstrated a clinical course of sustained recovery by the time they receive the first dose of study intervention
• Attends a daycare facility at least 3 days per week and 4 hours per day at which the participant would be in a contact group/playroom of at least one other child 6 to < 24 months of age who will participate in this study or is a member of a household, which includes at least one other child 6 to < 24 months of age who will participate in this study

Exclusion Criteria:

• 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
• 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 COVID-19 at the time of enrollment

• 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
• Member of a household that includes, or will include, an infant who is less than 6 months of age at the time of enrollment
• Attends a daycare facility and shares a daycare room with infants less than 6 months of age, and parent/legally acceptable representative is unable or unwilling to suspend attendance at the daycare facility for 28 days following study intervention administration
• Any need of supplemental oxygen therapy in a home or hospital setting at the time of enrollment.
• Participant's mother previous receipt or planned administration of an investigational RSV vaccine or any monoclonal antibody (such as Infliximab) during pregnancy and/or breastfeeding.

• Receipt or planned receipt of any of the following vaccines prior to or after the first study intervention administration:

  • any influenza vaccine within 7 days prior to and after, or any COVID-19 or inactivated vaccine or live-attenuated rotavirus vaccine within 14 days prior to and after, or
  • any live vaccine, other than rotavirus vaccine, within 28 days prior to and after
• Previous receipt of an investigational RSV vaccine or receiving any anti-RSV product (such as ribavirin or RSV Immunoglobulin (IG) or RSV monoclonal antibody) at the time of enrollment.
• 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
• Receipt at the time of enrollment or previous receipt of salicylate (aspirin) or salicylate-containing products
• Participation at the time of study enrollment (or in the 6 weeks preceding the first study intervention administration) or planned participation during the present study period in another clinical study investigating a vaccine, drug, medical device, or medical procedure
• 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 is not intended to contain all considerations relevant to a potential participation in a clinical trial.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: RSVt Vaccine Group; 2 intranasal administrations (56 days apart) of the RSVt vaccine at D01 and D57	Biological: RSVt Vaccine; Pharmaceutical Form: Suspension of virus in a nasal spray Route of Administration: Intranasal
Placebo Comparator: Control Group; 2 intranasal administrations (56 days apart) of the placebo at D01 and D57	Other: Control Group; Pharmaceutical Form: Suspension of virus in a nasal spray Route of Administration: Intranasal

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage of Placebo Receiving Pediatric Participants With Vaccine Virus Detected in Nasal Swabs After the First Vaccination	Nasal swabs were collected to assess the presence of vaccine virus after first vaccination. Vaccine virus transmission was defined as presence of detected vaccine virus confirmed by RSVt quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay (vaccine virus shedding >=lower limit of detection [LOD=2.80 log10 copies/mL]) in pediatric participants receiving placebo. Percentages are rounded off to the tenth decimal place.	Pre-vaccination on Day 1 and post-vaccination on Days 4, 8, 11, 15, 18 and 22
Titer of Vaccine Virus Shedding in All Pediatric Participants Detected in Nasal Swabs	Nasal swabs were collected to assess the shedding of the attenuated RSV vaccine strain and quantified by RSVt qRT PCR assay. Quantified virus shedding was defined as vaccine virus shedding >=lower limit of quantification (LLOQ=3.37 log10 copies/mL).	Pre-vaccination on Day 1 and post-vaccination on Days 4, 8, 11, 15, 18, 22, 64 and 71
Percentage of Placebo Receiving Pediatric Participants With Detected Shedding Who Showed Any Genetic Sequence Variation After Each Vaccination	Nasal swabs were collected to identify the difference in genetic sequence of mutated vaccine virus segments compared to the reference strain vaccine virus isolates in the vaccine virus positive swabs from pediatric participants receiving placebo after each vaccination. Detected virus shedding was defined as vaccine virus shedding >=LOD (2.80 log10 copies/mL).	Up to 21 days after each vaccination (Day 1 to Day 22 and Day 57 to Day 78)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Geometric Mean Titers (GMTs) of RSV A Serum Neutralizing Antibody (nAb) Titers	Serum samples were collected at specified timepoints for immunogenicity assessments. RSV A serum neutralizing antibody titers were evaluated by microneutralization (MN) assay.	Pre-vaccination on Day 1 (first vaccination) and Day 57 (second vaccination) and up to 28 days after second vaccination, Day 85
Secondary: Geometric Mean Titers of RSV Serum Anti-F Immunoglobulin G (IgG) Enzyme-linked Immuno-adsorbant Assay (ELISA) Antibody	Serum samples were collected at specified timepoints for immunogenicity assessments. Antibodies to RSV F antigen were measured using the anti RSV F IgG ELISA method.	Pre-vaccination on Day 1 (first vaccination) and Day 57 (second vaccination) and up to 28 days after second vaccination, Day 85
Number of Participants With Immediate Unsolicited 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.	Up to 30 minutes after each vaccination (Days 1 and 57)
Number of Participants With Solicited Administration Site Reactions and Systemic 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 and considered as related to the study vaccine administered. An administration site reaction was an AR at and around the administration/injection site and were commonly inflammatory reactions. Solicited systemic reactions were systemic AEs and those occurring during the specified collection period were always considered related to the vaccine even if there was evidence of alternative etiology.	Up to 21 days after each vaccination (Day 1 to Day 22 and Day 57 to Day 78)
Number of Participants With Unsolicited Adverse Events	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, that is, pre-listed in the CRF in terms of diagnosis and onset window post-vaccination.	Up to 28 days after each vaccination (Day 1 to Day 29 and Day 57 to Day 85)

Collaborators and Investigators

• Sponsor: Sanofi Pasteur, a Sanofi Company
• Investigators: Study Director: Clinical Sciences & Operations, Sanofi Pasteur, a Sanofi Company

Study record dates

Study Major Dates

• Study Start (Actual): February 6, 2023
• Primary Completion (Actual): December 27, 2024
• Study Completion (Actual): December 27, 2024

Study Registration Dates

• First Submitted: January 6, 2023
• First Submitted That Met QC Criteria: January 17, 2023
• First Posted (Actual): January 18, 2023

Study Record Updates

• Last Update Posted (Actual): January 26, 2026
• Last Update Submitted That Met QC Criteria: January 22, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Infections; RNA Virus Infections; Virus Diseases; Pneumovirus Infections; Paramyxoviridae Infections; Mononegavirales Infections; Respiratory Syncytial Virus Infections; Investigative Techniques; Epidemiologic Research Design; Epidemiologic Methods; Research Design; Methods; Control Groups
• Other Study ID Numbers: VAD00014; U1111-1278-3910 (Registry Identifier: ICTRP)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: 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

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No