An Extension and Crossover Vaccination Study on the Immune Response and Safety of a Vaccine Against Respiratory Syncytial Virus Given to Adults 60 Years of Age and Above Who Participated in RSV OA=ADJ-006 Study

Inclusion Criteria:

• Male or female participants who were previously enrolled in the RSV OA=ADJ-006 studyand received placebo (Placebo group) or a single dose of the RSVPreF3 OA vaccine (RSV_1dose group).

• Participants who, in the opinion of the investigator, can and will comply with therequirements of the protocol (e.g. completion of the diary cards, attend regularphone calls/study site visits, ability to access and utilize a phone or otherelectronic communications).

• Written or witnessed informed consent obtained from the participant prior toperformance of any study specific procedure.

• Participants who are medically stable in the opinion of the investigator at studyentry. Participants with chronic stable medical conditions with or without specifictreatment, such as diabetes, hypertension or cardiac disease, are allowed toparticipate in this study.

Exclusion Criteria:

Medical Conditions:

• Any confirmed or suspected immunosuppressive or immunodeficient condition resultingfrom disease or immunosuppressive/cytotoxic therapy based on medical history andphysical examination.

• History of any reaction or hypersensitivity likely to be exacerbated by anycomponent of the study intervention.

• Hypersensitivity to latex.

• Serious or unstable chronic illness.

• Recurrent or un-controlled neurological disorders or seizures.

• Significant underlying illness that in the opinion of the investigator would beexpected to prevent completion of the study.

• Any other medical condition that in the judgment of the investigator would makeintramuscular injection unsafe.

• Any other clinical condition that, in the opinion of the investigator, might poseadditional risk to the participant due to participation in the study.

• Any history of dementia or any medical condition that moderately or severely impairscognition and understanding of the informed consent form and/or study procedures.

• Participants who experienced an SAE or pIMD from first study interventionadministration in the RSV OA=ADJ-006 study until enrollment in this study that wasconsidered to be possibly or probably related to the study vaccine or non-studyconcomitant vaccines, either by the investigator or the sponsor, includinghypersensitivity reactions.

• Participants with a new onset of a pIMD or exacerbation of a pIMD from first studyintervention administration in the RSV OA=ADJ-006 study until enrollment in thisstudy, that, in the opinion of the investigator, exposes the participant tounacceptable risk from subsequent vaccination.

Prior/Concomitant Therapy:

• Use of any investigational or non-registered product other than the study vaccine during the period beginning 30 days before the first dose of study vaccine, or planned use during the study period. • Previous vaccination with an RSV vaccine (investigational or licensed vaccine) and/or planned administration of an RSV vaccine during the study period other than the RSVPreF3 OA vaccine administered during the RSV OA=ADJ-006 study.

Prior/Concurrent Clinical Study Experience:

• Concurrently participating in another clinical study, at any time during the study period, in which the participant has been or will be exposed to an investigational or a non-investigational vaccine/product.

Other Exclusion Criteria:

• History of chronic alcohol consumption and/or drug abuse as deemed by theinvestigator to render the potential participant unable/unlikely to provide accuratesafety reports or comply with study procedures.

• Participation of any study personnel or their immediate dependents, family, orhousehold members.

• Bedridden participants.

Specific exclusion criteria for Crossover group:

• Planned or administration of a vaccine not foreseen by the study protocol in the period starting 30 days before and ending 30 days after study intervention administration, with the exception of COVID vaccines which can be administered up to 14 days before or from 14 days after study vaccination. Inactivated seasonal influenza vaccines can be co-administered or administered at any time.

Specific exclusion criteria for RSV_PreS4, RSV_PreS5 and RSV_1Dose groups:

• Planned or administration of a vaccine not foreseen by the study protocol in theperiod starting 30 days before and ending 30 days after study interventionadministration, with the exception of COVID vaccines and inactivated seasonalinfluenza vaccines which can be administered up to 14 days before or from 14 daysafter study intervention administration.

• Administration of long-acting immune-modifying drugs or planned administration atany time during the study period.

• Administration of immunoglobulins and/or any blood products or plasma derivativesduring the period starting 90 days before the first study visit or plannedadministration during the study period.

• Chronic administration of immunosuppressants or other immunemodifying drugs duringthe period starting 90 days prior to the first study visit or planned administrationduring the study period. For corticosteroids, this will mean prednisone >= 20mg/day, or equivalent. Inhaled and topical steroids are allowed.