Flu Vaccines Work

While flu vaccine effectiveness can vary from season to season, flu vaccines provide important protections against flu every year.

Why CDC Estimates Vaccine Effectiveness (VE)

Learn more about why CDC studies flu vaccine effectiveness (VE) each season.

How CDC Estimates Vaccine Effectiveness (VE)

Learn about how CDC measures flu vaccine effectiveness (VE) to determine how well flu vaccines work.

Vaccine Effectiveness Networks

CDC uses several networks to estimate flu vaccine effectiveness against different flu-related outcomes like medical visits, hospitalizations, and intensive care unit (ICU) admissions.

A table with adjusted vaccine effectiveness estimates for flu seasons from 2004-2022 is available here.

Flu Vaccines Key Resources

CDC Seasonal Flu Vaccine Effectiveness Studies

Seasonal flu vaccine effectiveness bar chart, 2009-10 56%, 2010-11 60%, 2011-12 47%, 2012-13 49%, 2013-14 52%, 2014-15 19%, 2015-16 4%, 2016-17 40%, 2017-18 38%, 2018-1 29%, 2019-20 399%, 2020-21 no data, 2021-22 35%

CDC conducts studies each flu season to measure the benefits of seasonal flu vaccination.

Flu Burden Averted from Vaccination

Person after flu shot with band aid with text: #fightflu

CDC estimates the burden of flu and the impact of annual flu vaccination in the United States using a model that estimates the numbers of flu illnesses, medical visits, and hospitalization prevented by vaccination.

Resources for Health Professionals