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

The main purpose of this study is to learn about the effectiveness of Pfizer's ABRYSVO vaccine. This vaccine helps to prevent infections caused by Respiratory Syncytial Virus (RSV). RSV is a virus that can cause infections in the airways. These symptoms can be cold-like symptoms, but in some cases can lead to severe symptoms or hospitalization.

This study uses only healthcare data that are already collected from routine visits to healthcare providers. This means that participants will not be actively enrolled in the study and there are no study treatments. The study will look at data for about two years. This study will look at patient information from:

* Adults ages 60 years and older
* Adults who are eligible to receive the ABRYSVO vaccination

Substudy A:

* This study will assess the duration of protection of ABRYSVO in adults ages 60 years and older after completion of the original study.
* The substudy will look at data from subsequent RSV seasons after the first dose of ABRYSVO for about 3 years.

Substudy B:

* This study will assess vaccine effectiveness of ABRYSVO after revaccination in routine use, pending ACIP recommendation for revaccination.
* The substudy will look at data for about 2 years after revaccination.

The primary objective of this retrospective study is to estimate vaccine effectiveness of Pfizer's ABRYSVO vaccine against RSV-related lower respiratory tract disease (LRTD) requiring hospitalization among Kaiser Permanente Southern California members who are eligible for vaccination per current recommendations from the Advisory Committee on Immunization Practices (ACIP). Analyses will employ a retrospective case-control study with test negative design (TND) and a retrospective cohort design. The TND will assess RSV-related outcomes, while the cohort design will assess all-cause outcomes. The cohort study may also assess RSV-related outcomes, depending on RSV testing rates. Standard of care (SOC) RSV testing and re-testing of remnant SOC respiratory specimens for those who did not have SOC testing will be used to define RSV-related endpoints. For the cohort design, a sensitivity analysis including imputation of results for individuals experiencing lower respiratory tract disease without confirmation of RSV positivity or negativity may also be conducted. In the event that standard of care testing practices decline or there are not enough available specimens for estimating RSV-associated VE, the study may be extended to additional seasons. Secondary objectives of the TND, and if conducted for RSV-related endpoints, of the cohort study, include estimating vaccine effectiveness against: RSV-related LRTD hospitalizations among immunocompetent, RSV-related lower respiratory tract disease hospitalizations among high-risk groups, RSV-related acute respiratory tract infection hospitalizations, and Emergency Department (ED) visits. The retrospective cohort analysis will provide VE estimates against additional all-cause ARI and LRTD outcomes, as well as incidence rates and rate reductions for study outcomes, and will include outpatient outcomes. Analyses will include stratifications by presence of comorbidity, RSV subgroup, severity, age, frailty, and other selected demographic factors.

Eligibility Criteria:
Inclusion Criteria:

Test Negative Design:

1. KPSC patients eligible to receive ABRYSVO per current ACIP recommendations who are admitted to the hospital with ARI/LRTD, (defined using International Classification of Diseases (ICD) codes listed in Annex 2 Table 1) after start of study period, and who have had an RSV test, either through standard of care testing or blinded study testing of remnant respiratory specimens.
2. For secondary objectives estimating VE against ED admission, the TND will include KPSC patients eligible to receive ABRYSVO who present to the ED with ARI/LRTD after start of study period, and who have had an RSV test, either through standard of care testing or blinded study testing of remnant respiratory specimens.
3. For exploratory objectives estimating VE against RSV-related cardiac hospitalization, the TND will include KPSC patients eligible to receive ABRYSVO® who are hospitalized or present to the ED with cardiac events (defined using ICD codes listed in Annex 2 Table 3) after start of study period, and who have had an RSV test, either through SOC testing or blinded study testing of remnant respiratory specimens.
4. We will include membership requirement of 1 year prior to index date, which is defined as the date of hospitalization or ED admission (allowing 45-day administrative 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 facilitate accurate 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.