Past Seasons Vaccine Effectiveness Estimates
These pages include information about the estimated seasonal influenza vaccine effectiveness from past seasons, including tables of the estimated vaccine effectiveness (and 95% credible interval [Cr I]) by age group and virus subtype. Information on how these estimates are calculated can be found on CDC’s web page How CDC Estimates vaccine efficacy and effectiveness.
Table. Adjusted vaccine effectiveness estimates for influenza seasons from 2004-2022
CDC calculates vaccine effectiveness estimates through the U.S. VE Network
|
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 |
1914 |
37 |
22, 49 |
|
|
2008-09**† |
Unpublished |
WI, MI, NY, TN |
6713 |
41 |
30, 50 |
|
2009-10** |
WI, MI, NY, TN |
6757 |
56 |
23, 75 |
|
|
2010-11** |
WI, MI, NY, TN |
4757 |
60 |
53, 66 |
|
|
WI, MI, PA, TX, WA |
4771 |
47 |
36, 56 |
||
|
WI, MI, PA, TX, WA |
6452 |
49 |
43, 55 |
||
|
WI, MI, PA, TX, WA |
5999 |
52 |
44, 59 |
||
|
WI, MI, PA, TX, WA |
9311 |
19 |
10, 27 |
||
|
WI, MI, PA, TX, WA |
6879 |
48 |
41, 55 |
||
| Flannery 2018external icon | WI, MI, PA, TX, WA | 7410 |
40 |
32, 46 | |
| Rolfes 2019external icon | WI, MI, PA, TX, WA | 8,436 |
38 |
31, 43 | |
| Flannery 2019external icon | WI, MI, PA, TX, WA | 10,041 |
29 |
21, 35 | |
| Flannery, 2020external icon | WI, MI, PA, TX, WA | 8,845 |
39 |
32, 44 | |
| n/a | n/a | n/a |
n/a |
||
| Chung, 2022 | CA, MI, PA, TN, TX, WA, WI | 3.636 |
14 |
-17, 37 |
* 2020-2021 flu vaccine effectiveness was not estimated due to low flu virus circulation during the 2020-2021 flu season.
** From 2004-05 through 2010-11, the Flu VE Network also enrolled inpatients.
***Interim VE estimates
† Vaccine effectiveness (VE) estimates for the 2008-2009 flu season have not been published.
‡ Number of patients used in VE calculation.