Past Seasons’ Vaccine Effectiveness Estimates
These pages include information about the seasonal flu vaccine effectiveness estimates from past seasons, including tables of the estimated vaccine effectiveness (and 95% confidence interval [CI]) by age group and virus subtype. Information on how these estimates are calculated can be found on CDC’s web page How Flu Vaccine Effectiveness and Efficacy are Measured.
Table. Adjusted vaccine effectiveness estimates for influenza seasons from 2004-2024
Influenza Season† |
Reference |
Study Site(s) |
No. of Patients‡ |
Adjusted Overall VE (%) |
95% CI |
---|---|---|---|---|---|
2004-05* |
WI |
762 |
10 |
-36, 40 |
|
2005-06* |
WI |
346 |
21 |
-52, 59 |
|
2006-07* |
WI |
871 |
52 |
22, 70 |
|
2007-08* |
WI |
1,914 |
37 |
22, 49 |
|
2008-09*† |
Unpublished |
WI, MI, NY, TN |
6,713 |
41 |
30, 50 |
2009-10* |
WI, MI, NY, TN |
6,757 |
56 |
23, 75 |
|
2010-11* |
WI, MI, NY, TN |
4,757 |
60 |
53, 66 |
|
WI, MI, PA, TX, WA |
4,771 |
47 |
36, 56 |
||
WI, MI, PA, TX, WA |
6,452 |
49 |
43, 55 |
||
WI, MI, PA, TX, WA |
5,999 |
52 |
44, 59 |
||
WI, MI, PA, TX, WA |
9,311 |
19 |
10, 27 |
||
WI, MI, PA, TX, WA |
6,879 |
48 |
41, 55 |
||
Flannery 2018 | WI, MI, PA, TX, WA | 7,410 |
40 |
32, 46 | |
Rolfes 2019 | WI, MI, PA, TX, WA | 8,436 |
38 |
31, 43 | |
Flannery 2019 | WI, MI, PA, TX, WA | 10,041 |
29 |
21, 35 | |
Tenforde 2021 | WI, MI, PA, TX, WA | 8,845 |
39 |
32, 44 | |
n/a | n/a | n/a |
n/a |
||
Price 2022 | CA, MI, PA, TN, TX, WA, WI | 4,312 |
36 |
21, 48 | |
McLean 2023 | WI | 545 | 54 | 23, 73 | |
ACIP Presentation on February 28, 2024 [1.5 MB, 37 pages] | AZ, MI, MO, PA, OH, TX, WA | 3,394 | 42 | 29, 53 |
*From 2004-2005 through 2010-2011, the Flu VE Network also enrolled inpatients.
**2020-2021 flu vaccine effectiveness was not estimated due to low influenza virus circulation during the 2020-2021 flu season.
***In a Wisconsin study among patients aged 6 months to 64 years, VE was 54% against medically attended outpatient acute respiratory illness (ARI) associated with laboratory-confirmed influenza A virus infection.
†Vaccine effectiveness (VE) estimates for the 2008-2009 flu season have not been published.
‡Number of patients used in VE calculation.
††VE estimates for 2022-2023 flu season are preliminary.
****Overall VE was calculated for this table to be consistent with what has been reported historically and is available for comparison with historical estimates. All other 2023-2024 VE estimates are reported by age group.