Study of a Respiratory Syncytial Virus/Human Metapneumovirus Vaccine Candidate

Inclusion Criteria:

• Aged 60 years or older on the day of inclusion

• A female participant is eligible to participate if she is not pregnant orbreastfeeding and is of non-childbearing potential.

• Participants who are determined by medical history, physical examination (ifrequired), and clinical judgment of the investigator to be eligible for inclusionNote: Participants with pre-existing stable disease, defined as disease notrequiring significant change in therapy or hospitalization for worsening diseaseduring the 6 weeks before enrollment, can be included.

Exclusion Criteria:

Participants are excluded from the study if any of the following criteria apply:

• Any screening laboratory parameter with laboratory abnormalities deemed clinicallysignificant by the investigator

• Known or suspected congenital or acquired immunodeficiency; or receipt ofimmunosuppressive therapy. Persons living with stable human immunodeficiency virus (HIV) are not excluded

• Known systemic hypersensitivity to any of the study intervention components (eg,polyethylene glycol, polysorbate); history of a life-threatening reaction to thestudy interventions used in the study or to a product containing any of the samesubstances; any allergic reaction (eg, anaphylaxis) after administration of mRNAcoronavirus disease 2019 (COVID-19) vaccine

• History of RSV and/or hMPV-associated illness, diagnosed clinically, serologically,or microbiologically in the last 12 months

• Previous history of myocarditis, pericarditis, and/or myopericarditis

• Screening electrocardiogram 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 orstudy results

• Thrombocytopenia or bleeding disorder, contraindicating intramuscular (IM) injectionbased on investigator's judgment

• Receipt of anticoagulants in the 3 weeks preceding inclusion

• Chronic illness that, in the opinion of the investigator, is at a stage where itmight interfere with study conduct or completion

• Alcohol, prescription drug, or substance abuse that, in the opinion of theinvestigator, might interfere with the study conduct or completion

• History of acute infection symptoms or a positive severe acute respiratory syndromecoronavirus reverse transcription polymerase chain reaction (SARS-CoV-2 RT-PCR) orantigen test in the 10 days prior to the visit. A prospective participant should notbe included in the study until the condition has resolved

• Receipt of any vaccine other than mRNA vaccine in the 4 weeks preceding any studyintervention administration or planned receipt of any vaccine other than mRNAvaccine in the 4 weeks following any study intervention administration

• Receipt of any mRNA vaccine in the 60 days preceding any study interventionadministration or planned receipt of any mRNA vaccine in the 60 days following anystudy intervention administration

• Previous vaccination against RSV and/or hMPV (with a licensed or investigationalvaccine either as a monovalent vaccine or any combination of the antigens)

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

• Participation at the time of study enrollment (or in the 4 weeks preceding the firststudy intervention administration) or planned participation during the present studyperiod in another clinical study investigating a vaccine, drug, medical device, ormedical procedure The above information is not intended to contain allconsiderations relevant to a potential participation in a clinical trial.