Inclusion Criteria:

• Aged 60 years or older on the day of inclusion
• Non-childbearing potential (ie, post-menopausal for at least 1 year or surgically sterile)

Exclusion Criteria:

• History of laboratory-confirmed RSV and/or laboratory-confirmed HMPV infection affecting the participant and/or the participant's household in the previous 12 months
• Previous history of myocarditis, pericarditis, and/or myopericarditis
• Screening electrocardiogram (ECG) that is consistent with possible myocarditis, pericarditis, and/or myopericarditis or, in the opinion of the investigator, demonstrates clinically relevant abnormalities that may affect participant safety or study results
• Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with study conduct or completion
• Previous history of Guillain-Barré Syndrome
• Any vaccine given 4 weeks before or 4 weeks after study intervention
• Previous vaccination against RSV and/or HMPV with an investigational or marketed vaccine
• Receipt of any mRNA vaccine/product in the 2 months preceding study intervention administration
• Has received a blood transfusion or blood-derived products, including immunoglobulins, in the past 3 months
• Any screening laboratory parameter with laboratory abnormality > Grade 1 or deemed clinically significant by the investigator; if deemed appropriate, investigator may repeat these assessments

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