Influenza Vaccine and Associated Infection and Death in California, 2024 to 2025

Was influenza vaccination associated with protection against laboratory-confirmed influenza during the 2024 to 2025 season, and among infected persons, was influenza vaccination associated with protection against influenza-associated death?In a case-control study of linked diagnostic test results and immunization records for 1 106 628 California residents, influenza vaccination was associated with 40% lower likelihood of laboratory-confirmed influenza. Among adults aged 65 years and older with laboratory confirmed influenza, vaccination was associated with 29% lower likelihood of death due to influenza-related causes.These findings suggest influenza vaccination was associated with partial protection against illness and death caused by influenza viruses that circulated in California during the 2024 to 2025 influenza season.

Corresponding Author: Sophie Zhu, PhD, California Department of Public Health, 850 Marina Bay Pkwy, Richmond, CA 94804 (sophie.zhu@cdph.ca.gov).

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