Study of a Single Intramuscular Dose of Nirsevimab in the Prevention of Hospitalizations Due to Respiratory Syncytial Virus (RSV) Infection in Healthy Term and Preterm Infants During the First Year of Life

Inclusion Criteria:

• Born at ≥ 29 weeks gestational age and aged 0 to 12 months (calendar age), whoentered their first RSV season on the day of inclusion in the study (D01)

• Informed consent form was signed and dated by the parent(s) or other LAR(s) (and byan independent witness if required by local regulations)

• Participant and parent/LAR were able to attend the scheduled visit and to complywith all study procedures

Exclusion Criteria:

• Participants were not eligible for the study if any of the following criteria aremet:

• Known or suspected congenital or acquired immunodeficiency; or receipt ofimmunosuppressive 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 3months)

• Active confirmed RSV infection at the time of dosing/randomization

• Active LRTI at the time of dosing/randomization

• Known systemic hypersensitivity to any of the study intervention components, orhistory of a life-threatening reaction to the study intervention used in the studyor to a product containing any of the same substances

• Laboratory confirmed thrombocytopenia, or known thrombocytopenia, as reported by theparent/LAR, contraindicating intramuscular injection

• Bleeding disorder, or receipt of anticoagulants in the 3 weeks preceding inclusion,contraindicating intramuscular injection

• Any condition that, in the opinion of the investigator, is at a stage where it mightinterfere with study conduct or completion

• Moderate or severe acute illness/infection (according to investigator judgment) orfebrile illness (temperature ≥ 38.0°C [≥ 100.4°F]) on the day of study interventionadministration.

• A prospective participant was not included in the study until the condition hasresolved or the febrile event has subsided

• Mother of the infant participant was administered an RSV vaccine during herpregnancy with the infant participant

• Receipt of any monoclonal antibody by the infant participant

• Receipt of immune globulins, blood or blood-derived products in the past 3 months bythe infant participant

• Participation at the time of study enrollment or planned participation during thepresent study period in another clinical study investigating a vaccine, drug,medical device, or medical procedure

• Eligible to receive palivizumab at time of inclusion (as per local guidelines)

• In an emergency setting or hospitalized involuntarily

• Identified as a natural or adopted child of the Investigator or employee with directinvolvement in the proposed study

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