A Study to Learn About Revaccination With a Vaccine Called RSVpreF in Immunocompromised Adults

Key Inclusion Criteria: * Participants ≥18 years of age who are/were immunocompromised at the time of initial RSVpreF vaccination, per study protocol, and will be grouped based on prior RSV vaccination history: * Group 1 will include participants naïve to any RSV vaccine. * Group 2 will include participants who received a single prior dose of RSVpreF (Abrysvo) approximately 1 year (9 to 15 months) prior to enrollment. * Group 3 will include participants who received a single prior dose of RSVpreF (Abrysvo) approximately 2 years (21 to 27 months) prior to enrollment. * Group 4 will include participants who previously received 2 doses of RSVpreF in Study C3671023 Substudy B approximately 3 years (36 to 42 months) prior to enrollment. * Participants should have a life expectancy ≥12 months (365 days) in the opinion of the investigator at enrollment. Key Exclusion Criteria: * Prior history of any subtype of Guillain-Barré Syndrome (GBS) of any etiology. * History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (eg, anaphylaxis) to any components of the study intervention(s). * Participants with a history of transplant rejection, or PTLD, or participants who have had treatment for these conditions, within 90 days prior to study enrollment or suspected chronic humoral or cellular rejection. * Receipt of B-cell depleting therapies within 180 days prior to initial study vaccination. Refer to the study contact for further eligibility details.