A Study to Learn About ABRYSVO Vaccine in Older Adults to Prevent Severe Respiratory Syncytial Virus (RSV) Disease

Inclusion Criteria:

Test Negative Design:

1. KPSC patients eligible to receive ABRYSVO per current ACIP recommendations who areadmitted to the hospital with ARI/LRTD, (defined using International Classificationof Diseases (ICD) codes listed in Annex 2 Table 1) after start of study period, andwho have had an RSV test, either through standard of care testing or blinded studytesting of remnant respiratory specimens.

2. For secondary objectives estimating VE against ED admission, the TND will includeKPSC patients eligible to receive ABRYSVO who present to the ED with ARI/LRTD afterstart of study period, and who have had an RSV test, either through standard of caretesting or blinded study testing of remnant respiratory specimens.

3. For exploratory objectives estimating VE against RSV-related cardiachospitalization, the TND will include KPSC patients eligible to receive ABRYSVO® whoare hospitalized or present to the ED with cardiac events (defined using ICD codeslisted in Annex 2 Table 3) after start of study period, and who have had an RSVtest, either through SOC testing or blinded study testing of remnant respiratoryspecimens.

4. We will include membership requirement of 1 year prior to index date, which isdefined as the date of hospitalization or ED admission (allowing 45-dayadministrative gap), to facilitate accurate capture of comorbid conditions.

Retrospective Cohort Design:

1. All KPSC members eligible to receive ABRYSVO as of start of study period.

2. For the cohort study, patients must have at least 1 year of membership (allowing 45-day administrative gap) prior to start of study period (index date) to facilitateaccurate capture of comorbid conditions.

Exclusion Criteria:

Patients meeting any of the following criteria will not be included in the study:

Test Negative Design:

We will exclude patients who receive another licensed or investigational RSV vaccine prior to hospitalization or ED visit from the study population and analysis. Patients will be excluded if the index date is within certain time windows from vaccination date, outlined further in the exposure section below.

Cohort Design:

Patients will be excluded if they receive any other licensed or investigational RSV vaccine prior to study start; patients will be censored for receiving any other licensed or investigational RSV vaccine during the study period.

SSA and SSB Eligibility Criteria:

The inclusion criteria for Substudy A are described above for the Test Negative Design.