Table 4.
Estimated Vaccine Effectiveness Against Influenza A(H3N2)-Associated Hospitalization, US Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN), 2018-2019
| Characteristic | No. | Vaccinated Influenza-Positive Cases/ Total Influenza-Positive Cases (%) | Vaccinated Influenza-Negative Controls/ Total Influenza-Negative Controls (%) | Unadjusted VE (95% CI) | Adjusted VE (95% CI) |
|---|---|---|---|---|---|
| Alla,b | 2304 | 194/247 (79) | 1455/2057 (71) | –51 (–108 to –10) | –2 (–65 to 37) |
| By age groupc | |||||
| 18 to ≤56 yd,e | 771 | 50/66 (76) | 420/705 (60) | –112 (–279 to –18) | –130 (–374 to –27) |
| >56 to ≤69 yf,g | 769 | 54/80 (68) | 483/689 (70) | 11 (–45 to 46) | 42 (–23 to 72) |
| >69 yh,i | 764 | 90/101 (89) | 552/663 (83) | –65 (–218 to 15) | –1 (–182 to 64) |
| By influenza vaccination historyj | |||||
| Never/rarelyk,l | 490 | 7/38 (18) | 82/452 (18) | –4 (–132 to 60) | –1 (–191 to 65) |
| Always/almost alwaysm,n | 1665 | 182/200 (91) | 1301/1465 (89) | –27 (–118 to 22) | –16 (–105 to 34) |
Vaccination was defined as affirmative self-report with known or approximate date and location of vaccination provided and/or documented evidence of vaccination.
Abbreviations: CI, confidence interval; VE, vaccine effectiveness.
aVE adjusted for site, tertile of illness onset date relative to peak of influenza A(H3N2) cases, days between onset and specimen collection (<5 vs ≥5 days), age group, black race, frailty, current tobacco smoking (yes/no), diabetes/obesity/endocrine disorders, and influenza vaccination habit.
bData balanced on vaccination habit, age, number of high-risk conditions, home oxygen use, and ≥1 hospitalization in past year.
cDefined as tertiles of age in years in full dataset.
dVE adjusted for site, age, tertile of illness onset date relative to peak of influenza A(H3N2) cases, days between onset and specimen collection (<5 vs ≥5 days), black race, frailty, diabetes/obesity/endocrine disorders, and obstructive lung disorders.
eData balanced on vaccination habit, number of high-risk conditions, home oxygen use, ≥1 hospitalization in past year, and renal disorders.
fVE adjusted for age, tertile of illness onset date relative to peak of influenza A(H3N2) cases, days between onset and specimen collection (<5 vs ≥5 days), black race, frailty, and malignancy.
gData balanced on vaccination habit, number of high-risk conditions, metabolic disorder, home oxygen use, ≥1 hospitalization in past year, immunosuppression, and site.
hVE adjusted for age (continuous) tertile of illness onset date relative to peak of influenza A(H3N2) cases, days between onset and specimen collection, community dwelling, renal disorders, neurologic disorders, and home oxygen use.
iData balanced on vaccination habit, black race, current tobacco smoking (yes/no), site, and frailty.
jInfluenza vaccination history defined by patient self-report during enrollment interview; patients reporting vaccination history “sometimes” are excluded (n = 149).
kVE adjusted for tertile of illness onset date relative to peak of influenza A(H3N2) cases, days between onset and specimen collection, and frailty.
lData balanced on site, number of high-risk conditions, home oxygen use, ≥1 hospitalization in past year, black race, and immunosuppressive conditions.
mVE adjusted for tertile of illness onset date relative to peak of influenza A(H3N2) cases, days between onset and specimen collection, age (tertile), home oxygen use, site, number of high-risk conditions, ≥1 hospitalization in past year, black race, and immunosuppressive conditions.
nData balanced on age, black race, current tobacco smoking (yes/no), metabolic disorders and endocrine disorders, heart disease, and obstructive lung disorders.