Influenza outbreaks are a prevalent event in nursing homes (NHs). We will study baloxavir compared to oseltamivir when used for influenza prophylaxis when facilities identify an index incident case of influenza. This study will help guide nursing home's decision making and demonstrate the effectiveness of a novel antiviral for preventing influenza outbreaks.

A random study sample of about 1000 U.S. nursing homes (NHs), housing approximately 112,000 overall residents and 92,000 over the age of 65 years, of whom 64,500 are long-stay NH residents, will be recruited for the study. Participating facilities will be randomly allocated in a 1:1 ratio to oseltamivir or baloxavir for antiviral treatment and prophylaxis. Primary study data provided by facilities monthly during the influenza season will support primary and secondary endpoints along with administrative claims and public use datasets containing information on facility characteristics.

Inclusion Criteria:

- Medicare-certified NHs in any location in the United States with at least 50 long-stay residents 18 years of age or older.

Exclusion Criteria:

• Hospital-based facilities
• Facilities not submitting MDS data