Study overview

• 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 neutralizing antibody serostatus.
• To characterize the RSV-A serum neutralizing antibody responses to the study product in each vaccine group after vaccination in Respiratory Syncytial Virus (RSV) seronegative participants.

• To quantify the amount of vaccine virus shed by each participant by baseline neutralizing antibody serostatus.
• To determine the proportion of vaccinated infants and toddlers in each vaccine group infected with the vaccine virus after vaccination by baseline neutralizing antibody serostatus.
• To characterize the RSV-A serum neutralizing antibody responses to the study product in each vaccine group after vaccination in RSV seropositive participants.
• To characterize serum RSV-A anti-F immunoglobulin G antibody responses to the study product in each vaccine group after vaccination by baseline neutralizing antibody serostatus.
• To characterize serum RSV-A antibody responses (neutralizing and anti-F immunoglobulin G) to the study product in each vaccine group after the RSV season by baseline neutralizing antibody serostatus.

Eligibility

Inclusion criteria :

• 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

Exclusion criteria:

• 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.
• 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 or RSV monoclonal antibody).
• Receipt of immune globulins, blood or blood-derived products in the past 6 months prior to enrolment.
• 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.
  • 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 subject should not be included in the study until the condition has resolved or the febrile event has subsided.
• 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).
• 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.
• Any previous anaphylactic reaction.
• 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.
• 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).
• 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.
• 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.
• 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.
• Born at less than 34 weeks gestation.
• Born at less than 37 weeks gestation and less than 1 year of age at the time

The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.