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.
Started in 2003-04 and collects vaccine effectiveness data on outpatient illness with laboratory-confirmed flu.
Started in 2019 to collect data on how well flu vaccines work at preventing severe flu among intensive care unit (ICU) patients. As of April 1, 2021, IVY has expanded to also enroll all patients hospitalized with COVID-19. During the 2021-2022 flu season, the network will also enroll patients hospitalized with flu.
Started in 2015-16 and collects vaccine effectiveness data on pediatric hospitalizations with laboratory-confirmed flu in children 18 years of age and younger.
See Seasonal Influenza Vaccine Effectiveness, 2004-2021 for season-by-season data and references.