CDC’s Vaccine Effectiveness Networks

In the United States, CDC and the Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for all persons older than 6 months of age. Monitoring the performance of influenza vaccines is important for understanding and improving the benefits of vaccine. CDC uses four networks to estimate vaccine effectiveness (VE): the Flu VE Network, the Influenza Vaccine Effectiveness in the Critically Ill (IVY), the National Vaccine Surveillance Network (NVSN), and the VISION VE Network. The Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) was previously used to estimate VE among hospitalized adults but ended enrollment July 31, 2021. CDC will continue to collect information on adults hospitalized with influenza through its other VE networks.

See Seasonal Influenza Vaccine Effectiveness, 2004-2021 for season-by-season data and references.