At a glance
Inclusion Dates by Network
Network
Dates
October 1, 2024–February 4, 2025
October 2, 2024–January 30, 2025
October 1, 2024–January 17, 2025
October 1, 2024–January 24, 2025
Flu Vaccine Effectiveness for Children and Adults
Number and percentage of children and adolescents* (6 months to 17 years) and adults (18 years and older) receiving seasonal influenza vaccine, number and percentage with a positive or negative influenza test result, and vaccine effectiveness,† by influenza type and subtype§ — four vaccine effectiveness networks, United States, 2024–25 influenza season
| Network (Setting) | Influenza positive N vaccinated / Total (%) |
Influenza negative N vaccinated / Total (%) |
VE (95% CI) ¶ |
|---|---|---|---|
| All ages (aged ≥18 years) | |||
| Any** Influenza | |||
| VISION (outpatient) | 6,953/35,574 (20) | 31,785/103,984 (31) | 56 (54 to 58) |
| US Flu VE (outpatient) | 166/692 (24) | 848/2,652 (32) | 42 (29 to 54) |
| All children and adolescents aged <18 yrs | |||
| Any** Influenza | |||
| NVSN†† (outpatient§§) | 100/482 (21) | 855/2,487 (34) | 59 (47 to 68) |
| US Flu VE (outpatient) | 54/217 (25) | 256/917 (28) | 32 (1 to 54) |
| VISION (outpatient) | 1,322/9,563 (14) | 5,943/27,356 (22) | 60 (56 to 63) |
| NVSN (inpatient) | 28/119 (24) | 613/1,523 (40) | 63 (41 to 76) |
| VISION (inpatient) | 16/157 (10) | 406/1,481 (27) | 78 (60 to 89) |
| Influenza A(H1N1)pdm09 | |||
| NVSN (outpatient) | 32/224 (14) | 855/2,487 (34) | 72 (59 to 81) |
| US Flu VE (outpatient) | 9/50 (18) | 256/917 (28) | 53 (3 to 79) |
| NVSN (inpatient) | 13/60 (22) | 613/1,523 (40) | 63 (30 to 81) |
| Influenza A(H3N2) | |||
| NVSN (outpatient) | 62/218 (28) | 855/2,487 (34) | 42 (19 to 58) |
| US Flu VE (outpatient) | 29/107 (27) | 256/917 (28) | 16 (–34 to 49) |
| NVSN (inpatient) | 12/44 (27) | 613/1,523 (40) | 55 (14–77)¶¶ |
| All adults aged ≥18 yrs | |||
| Any¶ Influenza | |||
| US Flu VE (outpatient**) | 112/475 (24) | 592/1,735 (34) | 36 (16 to 51) |
| VISION (outpatient) | 5,631/26,011 (22) | 25,842/76,628 (34) | 54 (52 to 56) |
| IVY (inpatient) | 211/675 (31) | 873/2,500 (35) | 41 (28 to 52) |
| VISION (inpatient) | 905/2,959 (31) | 10,869/28,074 (39) | 55 (51 to 59) |
| Influenza A(H1N1)pdm09 | |||
| US Flu VE (outpatient) | 36/118 (31) | 592/1,735 (34) | 42 (8 to 64) |
| IVY (inpatient) | 12/50 (24) | 873/2,500 (35) | 39 (−14 to 67) |
| Influenza A(H3N2) | |||
| US Flu VE (outpatient) | 56/230 (24) | 592/1,735 (34) | 25 (–6 to 48) |
| IVY (inpatient) | 28/110 (26) | 873/2,500 (35) | 51 (22 to 69) |
| Adults aged 18–64 yrs | |||
| Any Influenza | |||
| US Flu VE (outpatient) | 84/419 (20) | 397/1,403 (28) | 37 (16 to 53) |
| VISION (outpatient) | 3,056/20,280 (15) | 10,864/49,103 (22) | 56 (53 to 58) |
| IVY (inpatient) | 61/334 (18) | 282/1,187 (24) | 48 (28 to 63) |
| VISION (inpatient) | 212/1,062 (20) | 1,966/8,803 (22) | 51 (41 to 59) |
| Adults aged ≥65 yrs | |||
| Any Influenza | |||
| US Flu VE (outpatient) | 28/56 (50) | 195/332 (59) | 18 (–69 to 60) |
| VISION (outpatient) | 2,575/5,731 (45) | 14,978/27,525 (54) | 51 (47 to 54) |
| IVY (inpatient) | 150/341 (44) | 591/1,313 (45) | 38 (19 to 52) |
| VISION (inpatient) | 693/1,897 (37) | 8,903/19,271 (46) | 57 (52 to 61) |
*Aged 6 months–17 years (NVSN and VISION); 8 months–17 years (US Flu VE).
† VE was estimated using the test-negative design comparing odds of receipt of 2024–2025 influenza vaccination among persons with an acute respiratory illness who received a positive influenza test result with those among persons who received a negative influenza or SARS-CoV-2 test result. ORs were estimated using logistic regression; VE was calculated as (1 − adjusted OR) × 100%. Firth logistic regression was used for estimates from IVY.
§ Subtype was not available for VISION.
¶ All networks were adjusted for geographic region, age, and calendar time. IVY, US Flu VE, and VISION were adjusted for sex and race and ethnicity.
** As of February 1, 2025, most influenza viruses detected have been influenza A viruses (97% of positive specimens).
†† Patients enrolled as outpatients in NVSN might have progressed to a more acute level of care, and those data might not be reflected in this analysis.
§§ Outpatient = outpatient clinics, urgent care, and emergency departments (NVSN and US Flu VE); or urgent care and emergency departments (VISION).
¶¶ Firth logistic regression was used for this estimate.
- Frutos AM, Cleary S, Reeves EL, et al. Interim Estimates of 2024–2025 Seasonal Influenza Vaccine Effectiveness — Four Vaccine Effectiveness Networks, United States, October 2024–February 2025. MMWR Morb Mortal Wkly Rep 2025;74:83–90. DOI: http://dx.doi.org/10.15585/mmwr.mm7406a2.