What to know
Background
For more than a decade, CDC has used a model to estimate the annual number of flu illnesses, medical visits, hospitalizations, and deaths during the flu season, and to estimate the impact that flu vaccination had on illness outcomes in the United States123456. The methods used to calculate the estimates of flu burden prevented by flu vaccination have been described previously16. CDC uses the estimates of the impact of flu vaccination to inform policy and communications promoting vaccination as the best way to prevent flu.
CDC estimates that during the 2023-2024 season, flu vaccination prevented 9.8 million flu-related illnesses, 4.8 million medical visits, 120,000 hospitalizations, and 7,900 deaths.
Estimated Number of Flu-Related Illnesses, Medical Visits, Hospitalizations, and Deaths Prevented by Vaccination, by Age Group—United States, 2023-2024 Flu Season
| Symptomatic Illnesses | Medical Visits | Hospitalizations | Deaths | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Age group | Vaccine Coverage (%) | Adjusted VE (95% CI) | Inpatient Adjusted VE (95% CI) | Estimate | 95% UI | Estimate | 95% UI | Estimate | 95% UI | Estimate | 95% UI | |
| 6 months-4 years | 63.5% | 65% (64.7, 65.3) | 71.8% (71.3, 72.2) | 1,422,807 | (1,084,091, 2,429,071) | 953,281 | (722,949, 1,630,197) | 11,663 | (8,843, 19,942) | 173 | (37, 482) | |
| 5-17 years | 52.6% | 52% (51.8, 52.2) | 51% (50.7, 51.4) | 3,098,105 | (2,306,816, 7,218,811) | 1,611,014 | (1,187,172, 3,793,928) | 8,283 | (6,171, 19,309) | 93 | (25, 415) | |
| 18-49 years | 32.4% | 51.4% (51.1, 51.6) | 51.8% (51.5, 52) | 2,729,736 | (1,843,164, 7,126,831) | 1,010,002 | (672,347, 2,650,698) | 15,463 | (10,441, 40,391) | 513 | (142, 1,784) | |
| 50-64 years | 45.9% | 40.9% (40.5, 41.2) | 42.3% (42.1, 42.6) | 1,757,607 | (1,237,781, 4,206,912) | 755,771 | (527,270, 1,817,548) | 19,447 | (13,693, 46,531) | 1,311 | (358, 3,795) | |
| 65+ years | 69.1% | 37.4% (37.1, 37.7) | 34.5% (34.3, 34.7) | 779,211 | (524,520, 1,930,185) | 436,358 | (291,321, 1,081,948) | 63,930 | (43,084, 158,152) | 5,815 | (2,259, 41,310) | |
| All ages | 49.9% (49.7, 50) | 40.1% (40, 40.2) | 9,787,466 | (8,133,904, 16,881,781) | 4,766,427 | (3,980,513, 8,094,186) | 118,786 | (94,989, 223,408) | 7,905 | (4,003, 43,636) | ||
Additional information about How CDC Estimates the Burden of Flu Prevented by Vaccination and the 2023-2024 Burden Prevented by Vaccination can be found in the 2023-2024 Influenza Activity report.
- Kostova D, Reed C, Finelli L, Cheng PY, Gargiullo PM, Shay DK, et al. Influenza Illness and Hospitalizations Averted by Influenza Vaccination in the United States, 2005-2011. PLoS One. 2013;8(6):e66312.
- Reed C, Chaves SS, Daily Kirley P, Emerson R, Aragon D, Hancock EB, et al. Estimating influenza disease burden from population-based surveillance data in the United States. PLoS One. 2015;10(3):e0118369.
- Centers for Disease Control and Prevention. Estimated influenza illnesses and hospitalizations averted by influenza vaccination – United States, 2012-13 influenza season. MMWR Morb Mortal Wkly Rep. 2013 Dec 13;62(49):997-1000.
- Reed C, Kim IK, Singleton JA, Chaves SS, Flannery B, Finelli L, et al. Estimated influenza illnesses and hospitalizations averted by vaccination–United States, 2013-14 influenza season. MMWR Morb Mortal Wkly Rep. 2014 Dec 12;63(49):1151-4.
- Centers for Disease Control and Prevention. Estimated Influenza Illnesses and Hospitalizations Averted by Vaccination — United States, 2014–15 Influenza Season. 2015 December 10, 2015 [cited 2016 October 27]; Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4584537/
- Tokars JI, Rolfes MA, Foppa IM, Reed C. An evaluation and update of methods for estimating the number of influenza cases averted by vaccination in the United States. Vaccine. 2018 Nov 19;36(48):7331-7.