An AE is any untoward medical occurrence in a participant or in a clinical investigation participant administered a medicinal product and which does not necessarily have a causal relationship with this treatment. An unsolicited AE is an observed AE that does not fulfill the conditions pre-listed in the case report book (CRB) in terms of diagnosis and/or onset window post-vaccination. Systemic AEs are all AEs that were not injection or administration site reactions. Immediate events are recorded to capture medically relevant unsolicited systemic AEs (including those related to the product administered) that occur within the first 30 minutes after vaccination.

All noxious and unintended responses to a medicinal product related to any dose are considered adverse reactions (AR). A solicited reaction is an "expected" AR (sign or symptom) observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRB. An administration site reaction is an AR at and around the administration site. Systemic ARs are all ARs that are not injection or administration site reactions.

An AE is any untoward medical occurrence in a participant or in a clinical investigation participant administered a medicinal product and which does not necessarily have a causal relationship with this treatment. An unsolicited AE is an observed AE that does not fulfill the conditions pre-listed in the CRB in terms of diagnosis and/or onset window post-vaccination.

An AESI is one of scientific and medical concern specific to the Sponsor's product or program, for which ongoing monitoring and rapid communication by the investigator to the sponsor can be appropriate.

An MAAE is a new onset or a worsening of a condition that prompts the participant or participant's parent/guardian/legally authorized representative to seek unplanned medical advice at a physician's office or Emergency Department.

An SAE is any untoward medical occurrence that at any dose results in death or is life-threatening or requires inpatient hospitalization or prolongation of existing hospitalization or results in persistent or significant disability/incapacity or is a congenital anomaly/birth defect or is an important medical event.

RSV A neutralizing antibody measured by microneutralization. RSV-naïve participants are defined as undetectable serum anti-RSV A IgA antibodies.