Influenza Activity and Estimated Vaccine Effectiveness During the 2025-2026 Influenza Season

How severe is the 2025-2026 US influenza season, and are existing mitigation measures, such as antivirals and vaccines, effective?This surveillance study of influenza data from September 2025 through March 2026 indicated a moderately severe influenza season during which antigenically drifted A(H3N2) viruses predominated but influenza antiviral medications and vaccines were still estimated to be effective.These findings highlight that monitoring influenza activity is critical for understanding the risk and burden of influenza and the benefits of existing interventions.

Corresponding Author: Eduardo Azziz-Baumgartner, MD, Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, MS A32, Atlanta, GA 30333 (Eha9@cdc.gov).

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