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.
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1. Vaccine Effectiveness (VE) calculated as 1 minus the odds ratio (OR) comparing the odds of being vaccinated with ABRYSVO for RSV-related hospitalized LRTD cases and controls, multiplied by 100%.
Timeframe: Up to 2 years