Interim US Flu Vaccine Effectiveness (VE) Data for 2021-2022
Limited flu circulation this season made it challenging to evaluate vaccine effectiveness, but these preliminary, interim estimates indicate that flu vaccine provided important health benefit this season, reducing the risk of illness with H3N2 viruses by about one-third, even though some of the circulating H3N2 viruses were antigenically different from the vaccine virus. Final vaccine effectiveness estimates will include information on how well 2021-22 flu vaccine protected against severe flu illness and will be published later this year.
Description of patients enrolled in the US Flu VE Network, 2021-2022
Total respondents: 4705*
*Note: 2046 persons who were SARS-CoV-2 positive were excluded.
| Age | Number | % Total |
|---|---|---|
| 6 months-17 years | 1487 | 32 |
| 18-49 years | 1983 | 42 |
| 50 years and older | 1235 | 26 |
| Flu type | Flu-positive | Flu-negative | Adjusted Interim VE* | ||||
|---|---|---|---|---|---|---|---|
| Total | Vaccinated no. (%) |
Total | Vaccinated no. (%) |
% | Confidence Interval | ||
| Flu A | |||||||
| Overall | 487 | 210 (43%) | 4,249 | 2,501 (59%) | 34 | (19–46) | |
| Flu A (H3N2) | |||||||
| Overall | 456 | 191 (42%) | 4,249 | 2,501 (59%) | 35 | (19–47) | |
Abbreviations: VE = vaccine effectiveness.
| Flu type | Flu-positive | Flu-negative1 | Adjusted Interim VE2 | ||||
|---|---|---|---|---|---|---|---|
| Total | Vaccinated no. (%) |
Total | Vaccinated no. (%) |
% | Confidence Interval | ||
| Influenza A(H3N2) | |||||||
| Overall | 456 | 191 (42%) | 4,249 | 2,501 (59%) | 35 | (19–47) | |
| 6 mos – 17 years | 221 | 76 (34%) | 1,266 | 650 (51%) | 44 | (22–60) | |
| 18 – 49 years | 168 | 71 (42%) | 1,815 | 998 (55%) | 27 | (-3–48) | |
| 50 years and older | 67 | 44 (66%) | 1,168 | 853 (73%) | NR3 | ||
1 Persons testing negative for both influenza and SARS-CoV-2 using molecular assays.
2 Multivariable logistic regression models adjusted for site, age, month of onset, self-rated general health status, and race/ethnicity.
3 Not reported due to insufficient data for patients aged ≥50 years.
