The study will evaluate the immune response of the RSVPreF3 OA investigational vaccine in Chinese adults 18 to 59 years of age (YOA) who are at increased risk of respiratory syncytial virus (RSV) disease, in comparison with the immune response generated in older adults 60 YOA and above from the 219815 (RSV OA=ADJ-021; NCT06551181) study following a single dose of the RSVPreF3 OA vaccine. In addition, the safety and reactogenicity of the vaccine will also be assessed.
Participants who, in the opinion of the investigator, can and will comply with the requirements of the protocol.
Written or witnessed informed consent obtained from the participant (participant must be able to understand the informed consent) prior to performance of any study-specific procedure.
A male or female participant 18-59 YOA at the time of the study intervention administration.
A stable condition is defined as a disease not requiring significant change (based on the investigator's opinion) in therapy or worsening during the 3 months before enrollment.
Any confirmed or suspected immunosuppressive or immunodeficient condition resulting from disease or immunosuppressive/cytotoxic therapy, based on medical history and physical examination.
History of any reaction or hypersensitivity likely to be exacerbated by any component of the study intervention
Unstable chronic illness.
Any history of dementia or any medical condition that moderately or severely impairs cognition.
Parallel
RSVPreF3 OA vaccine
Biological/Vaccine1 dose of RSVPreF3 OA investigational vaccine administered intramuscularly in the deltoid region of the non-dominant arm.
Placebo
Biological/Vaccine1 dose of saline solution administered intramuscularly in the deltoid region of the non-dominant arm.
RSV-A neutralizing titers expressed as group Geometric Mean Titers (GMTs)
The serum neutralizing titers are expressed in Estimated Dilution (ED60). The group GMT ratio will be evaluated for RSV-OA overseas group (from RSV OA-ADJ-021 study) over RSV AIR (from the current study).
RSV-A neutralizing titers expressed as group Seroresponse rate (SRR)
The SRR is defined as the proportion of participants having a 4-fold increase in neutralizing titers. The group SRR difference will be evaluated for RSV-OA overseas group (from RSV OA-ADJ-021 study) minus RSV AIR (from the current study).
RSV-B neutralizing titers expressed as group GMTs
The serum neutralizing titers are expressed in ED60. The group GMT ratio will be evaluated for RSV-OA overseas group (from RSV OA-ADJ-021 study) over RSV AIR (from the current study).
RSV-B neutralizing titers expressed as group SRR
The group SRR difference will be evaluated for RSV-OA overseas group (from RSV OA-ADJ-021 study) minus RSV AIR (from the current study).
RSV-A and RSV-B neutralizing titers expressed as group GMTs
The serum neutralizing titers are expressed in ED60. The group GMT ratio will be evaluated for RSV-OA Chinese group (from RSV OA-ADJ-021 study) over RSV AIR (from the current study).
RSV-A and RSV-B neutralizing titers expressed as group SRR
The group SRR difference will be evaluated for RSV-OA Chinese group (from RSV OA-ADJ-021 study) minus RSV AIR (from the current study).
Number of participants with RT-PCR-confirmed RSV A and/or B-associated acute respiratory illness (ARI) and lower respiratory tract disease (LRTD), assessed for all groups of the current study
An ARI is defined as the presence of at least 2 respiratory symptoms/signs for at least 24 hours; or at least 1 respiratory symptom/sign and 1 systemic symptom/sign for at least 24 hours. An RT-PCR-confirmed RSV-ARI is an event meeting the case definition of ARI with at least one RSV-positive swab detected by RT-PCR. A LRTD is defined as the presence of at least 2 lower respiratory symptoms/signs for at least 24 hours including at least 1 lower respiratory sign; or at least 3 lower respiratory symptoms for at least 24 hours. An RT-PCR-confirmed RSV-LRTD is an event meeting the case definition of LRTD with at least one RSV-positive swab detected by RT-PCR.
Duration of RT-PCR-confirmed RSV A and/or B-associated ARI and LRTD episodes, assessed for all the groups of the current study
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