RSV Vaccination in Immunocompromised Patients.

General inclusion criteria 1. Participants who, in the opinion of the investigator, can understand and will comply with the requirements of the protocol. 2. Participants living in the general community or in an assisted-living facility that provides minimal assistance can be enrolled, such that the participant is primarily responsible for self-care and activities of daily living. 3. Participants who can give written informed consent prior to study entry and performance of any study-specific procedure. 4. Female participants of non-childbearing potential may be enrolled in the study. Non-childbearing potential is defined as hysterectomy, post-menopause, premenarche, bilateral oophorectomy, or bilateral salpingectomy 5. Female participants of childbearing potential may be enrolled in the study if the participant has practiced adequate contraception from 1 month prior to first Arexvy vaccination and agreed to continue adequate contraception for at least 1 month after completion of the last study intervention administration, and has a negative pregnancy test on the day of first vaccination prior to vaccine application. 6. Participants with chronic medical conditions with or without specific treatment are allowed to participate in this study if considered by the investigator as medically stable. 7. Additional inclusion criteria for "group 1": 7.1. Age ≥18 years at the time of signing the Informed consent form (ICF). 7.2. Diagnosis of a hemato-oncological disease: multiple myeloma including early stage disease or lymphoma in participants medically stable in the opinion of the investigator at study inclusion. 7.3. Participants without SCT or ≥3 months after autologous SCT until 24 months after SCT. SCT \>24 months, if they have ongoing immunomodulatory/suppressive treatment. 7.4. Immunosuppressive or modulating medication related to the hemato-oncological disease are allowed. 8. Additional inclusion criteria for "group 2": 8.1. Age ≥18 years at the time of signing the Informed consent form (ICF). 8.2. Diagnosis of lung cancer ≥ stage 1. 8.3. Ongoing cancer treatment (including chemotherapy and immunotherapy) or initiation planned within 14 days and treatment initiation/vaccinations preferentially scheduled between treatment cycles. 9. Additional inclusion criteria for "group 3": 9.1. Age ≥18 years at the time of signing the Informed consent form (ICF). 9.2. Diagnosis of an autoimmune/chronic inflammatory disease with chronic inflammatory bowel disease (IBD) or rheumatoid arthritis (RA). 9.3. Treatment with biologicals such as TNF-alpha blocker, anti-CD20, JAK-inhibitors or other biological treatment (combinations with DMARDs, immunomodulators or steroidal or non-steroidal anti-inflammatory drugs are allowed). 9.4. Stable disease at time of study entry. 10. Additional inclusion criteria for "group 4": 10.1. Age ≥60 years at the time of signing the Informed consent form (ICF). 10.2. Healthy, as established by medical history before entering the study with medically stable/controlled chronic conditions such as diabetes, hypertension or cardiac disease allowed.