Prospective Surveillance of Respiratory Syncytial Virus Disease in Infants and Toddlers

Inclusion Criteria: * Aged 6 months to \< 22 months on the day of inclusion (means the day of the 6-month birthday to the day before the 22-month 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 are enrolled in the 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) * Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with study conduct or completion * 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 human immunodeficiency virus (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 * Participant's mother 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: * Any intranasal live attenuated vaccine within the 28 days prior to enrollment * Any injectable live attenuated vaccine within the 28 days prior to and after enrollment * Previous receipt of an investigational RSV vaccine or receiving any anti-RSV product (such as ribavirin or RSV immune globulin or RSV monoclonal antibody) less than 6 months before enrollment * Receipt of immune globulins, blood or blood-derived products in the past 3 months * 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 The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial