What to know
Past Seasons Estimates
|
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Unpublished |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 | |
| Chung 2024 | MI, PA, TX, WA, AZ, MO, OH | 2,561 | 30 | -9, 54 | |
| Chung 2025 | AZ, MI, MO, PA, OH, TX, WA | 9,061 | 44 | 36, 51 | |
| Frutos 2025 | MN, WI, UT, CA, OR, WA, IN, CO | 139,558 | 56 | 54, 58 |
*From 2004-2005 through 2010-2011, the Flu VE Network also enrolled inpatients.
†Vaccine effectiveness (VE) estimates for the 2008-2009 flu season have not been published.
**2020-2021 flu vaccine effectiveness was not estimated due to low influenza virus circulation during the 2020-2021 flu season.
‡Number of patients used in VE calculation.
***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.
††VE estimates for 2024-2025 flu season are preliminary.
Information on how these estimates are calculated can be found on CDC's web page How Flu Vaccine Effectiveness and Efficacy are Measured.