Table 3.
Characteristics of Vaccinated and Unvaccinated Study Participants by Age Group, US Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN), 2018–2019 (N = 2863)
| Characteristic | All (N = 2863) | Patients Aged 18 to ≤56 y (n = 968) | Patients Aged >56 to ≤69 y (n = 968) | Patients Aged >69 y (n = 927) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Vaccinateda | Unvaccinated | P Valueb | Standardized Differencec | Vaccinateda | Unvaccinated | P Valueb | Standardized Differencec | Vaccinateda | Unvaccinated | P Valueb | Standardized Differencec | Vaccinateda | Unvaccinated | P Valueb | Standardized Differencec | |
| No. | 1991 | 872 | 563 | 405 | 660 | 308 | 768 | 159 | ||||||||
| Site | .801 | 0.04 | .205 | 0.14 | .225 | 0.15 | .123 | 0.22 | ||||||||
| Central Texas | 609 (30.6) | 277 (31.8) | 112 (19.9) | 102 (25.2) | 178 (27.0) | 96 (31.2) | 319 (41.5) | 79 (49.7) | ||||||||
| Southeast Michigan | 479 (24.1) | 217 (24.9) | 160 (28.4) | 116 (28.6) | 176 (26.7) | 81 (26.3) | 143 (18.6) | 20 (12.6) | ||||||||
| Western Pennsylvania | 562 (28.2) | 234 (26.8) | 177 (31.4) | 117 (28.9) | 206 (31.2) | 78 (25.3) | 179 (23.3) | 39 (24.5) | ||||||||
| Central Tennessee | 341 (17.1) | 144 (16.5) | 114 (20.2) | 70 (17.3) | 100 (15.2) | 53 (17.2) | 127 (16.5) | 21 (13.2) | ||||||||
| Baseline characteristics | ||||||||||||||||
| Demographics and behavioral risk factors | ||||||||||||||||
| Age group | <.001 | 0.50 | ||||||||||||||
| 18 to ≤56 y | 563 (28.3) | 405 (46.4) | 563 (100.0) | 405 (100.0) | … | … | … | … | ||||||||
| >56 to ≤69 y | 660 (33.1) | 308 (35.3) | … | … | 660 (100.0) | 308 (100.0) | … | … | ||||||||
| >69 y | 768 (38.6) | 159 (18.2) | … | … | … | … | 768 (100.0) | 159 (100.0) | ||||||||
| Age, y, mean (SD) | 63.79 (16.48) | 56.03 (15.63) | <.001 | 0.48 | 43.20 (10.84) | 42.77 (10.51) | .535 | 0.04 | 63.05 (3.61) | 62.33 (3.62) | .004 | 0.20 | 79.52 (6.91) | 77.63 (6.45) | .002 | 0.28 |
| Female sex | 1112 (55.9) | 487 (55.8) | 1 | <0.001 | 323 (57.4) | 224 (55.3) | .567 | 0.04 | 358 (54.2) | 168 (54.5) | .985 | 0.01 | 431 (56.1) | 95 (59.7) | .452 | 0.07 |
| Black race | 441 (22.1) | 324 (37.2) | <.001 | 0.33 | 184 (32.7) | 176 (43.5) | .001 | 0.22 | 174 (26.4) | 110 (35.7) | .004 | 0.20 | 83 (10.8) | 38 (23.9) | <.001 | 0.35 |
| Community dwelling | 1871 (94.0) | 830 (95.2) | .229 | 0.05 | 539 (95.7) | 384 (94.8) | .605 | 0.04 | 636 (96.4) | 301 (97.7) | .354 | 0.08 | 696 (90.6) | 145 (91.2) | .94 | 0.02 |
| Insured | 1920 (96.4) | 790 (90.6) | <.001 | 0.24 | 521 (92.5) | 350 (86.4) | .003 | 0.20 | 635 (96.2) | 283 (91.9) | .007 | 0.18 | 764 (99.5) | 157 (98.7) | .609 | 0.08 |
| Current tobacco smoking | 429 (21.5) | 314 (36.0) | <.001 | 0.32 | 185 (32.9) | 167 (41.2) | .009 | 0.17 | 173 (26.2) | 120 (39.0) | <.001 | 0.28 | 71 (9.2) | 27 (17.0) | .006 | 0.23 |
| Current vaping/e-cigarette use | 92 (4.6) | 59 (6.8) | .023 | 0.09 | 51 (9.1) | 41 (10.1) | .655 | 0.04 | 33 (5.0) | 15 (4.9) | 1 | 0.01 | 8 (1.0) | 3 (1.9) | .622 | 0.07 |
| Comorbid health conditionsd | ||||||||||||||||
| Obstructive lung disease | 1002 (50.3) | 419 (48.1) | .28 | 0.05 | 276 (49.0) | 186 (45.9) | .375 | 0.06 | 384 (58.2) | 148 (48.1) | .004 | 0.20 | 342 (44.5) | 85 (53.5) | .049 | 0.18 |
| Nonobstructive lung disease | 866 (43.5) | 314 (36.0) | <.001 | 0.15 | 229 (40.7) | 115 (28.4) | <.001 | 0.26 | 296 (44.8) | 123 (39.9) | .171 | 0.10 | 341 (44.4) | 76 (47.8) | .486 | 0.07 |
| Heart disease | 1291 (64.8) | 460 (52.8) | <.001 | 0.25 | 291 (51.7) | 164 (40.5) | .001 | 0.23 | 436 (66.1) | 171 (55.5) | .002 | 0.22 | 564 (73.4) | 125 (78.6) | .207 | 0.12 |
| Congestive heart failure | 674 (33.9) | 227 (26.0) | <.001 | 0.17 | 130 (23.1) | 72 (17.8) | .054 | 0.13 | 223 (33.8) | 82 (26.6) | .031 | 0.16 | 321 (41.8) | 73 (45.9) | .386 | 0.08 |
| Neurologic disorder | 722 (36.3) | 226 (25.9) | <.001 | 0.23 | 191 (33.9) | 85 (21.0) | <.001 | 0.29 | 238 (36.1) | 82 (26.6) | .005 | 0.21 | 293 (38.2) | 59 (37.1) | .875 | 0.02 |
| Renal disorders | 846 (42.5) | 305 (35.0) | <.001 | 0.16 | 219 (38.9) | 115 (28.4) | .001 | 0.22 | 281 (42.6) | 110 (35.7) | .05 | 0.14 | 346 (45.1) | 80 (50.3) | .261 | 0.11 |
| Malignancy | 493 (24.8) | 170 (19.5) | .002 | 0.13 | 68 (12.1) | 40 (9.9) | .332 | 0.07 | 162 (24.5) | 77 (25.0) | .942 | 0.01 | 263 (34.2) | 53 (33.3) | .898 | 0.02 |
| Hematologic disorders | 225 (11.3) | 88 (10.1) | .374 | 0.04 | 82 (14.6) | 36 (8.9) | .01 | 0.18 | 74 (11.2) | 39 (12.7) | .584 | 0.05 | 69 (9.0) | 13 (8.2) | .862 | 0.03 |
| Metabolic disorders | 1233 (61.9) | 392 (45.0) | <.001 | 0.35 | 246 (43.7) | 135 (33.3) | .001 | 0.21 | 438 (66.4) | 154 (50.0) | <.001 | 0.34 | 549 (71.5) | 103 (64.8) | .112 | 0.14 |
| Diabetes/obesity/endocrine disorders | 1539 (77.3) | 562 (64.4) | <.001 | 0.29 | 385 (68.4) | 227 (56.0) | <.001 | 0.26 | 532 (80.6) | 208 (67.5) | <.001 | 0.30 | 622 (81.0) | 127 (79.9) | .83 | 0.03 |
| Health status indicators | ||||||||||||||||
| Number of ACIP high-risk conditions, mean (SD) | 5.66 (3.27) | 4.54 (3.13) | <.001 | 0.35 | 5.08 (3.35) | 3.73 (2.95) | <.001 | 0.43 | 5.98 (3.18) | 4.88 (3.17) | <.001 | 0.35 | 5.81 (3.22) | 5.92 (2.90) | .692 | 0.04 |
| Charlson Comorbidity Index, mean (SD) | 3.23 (3.02) | 2.69 (2.90) | <.001 | 0.18 | 2.69 (2.78) | 2.13 (2.63) | .001 | 0.21 | 3.37 (2.96) | 2.90 (2.95) | .021 | 0.16 | 3.50 (3.19) | 3.72 (3.13) | .412 | 0.07 |
| Frailty score (0–5), mean (SD) | 2.01 (1.45) | 1.86 (1.52) | .016 | 0.10 | 1.81 (1.38) | 1.64 (1.44) | .064 | 0.12 | 2.07 (1.48) | 1.93 (1.51) | .191 | 0.09 | 2.10 (1.45) | 2.30 (1.61) | .122 | 0.13 |
| Home oxygen use | 600 (30.4) | 162 (18.7) | <.001 | 0.28 | 150 (26.7) | 59 (14.7) | <.001 | 0.30 | 228 (35.1) | 68 (22.1) | <.001 | 0.29 | 222 (29.1) | 35 (22.0) | .086 | 0.16 |
| ≥1 hospitalization in prior year (self-report) | 1259 (63.2) | 477 (54.7) | <.001 | 0.17 | 393 (69.8) | 223 (55.1) | <.001 | 0.31 | 437 (66.2) | 160 (51.9) | <.001 | 0.29 | 429 (55.9) | 94 (59.1) | .505 | 0.07 |
| Self-reported chemotherapy/radiation, immunosuppressive medications | 824 (41.4) | 290 (33.3) | <.001 | 0.17 | 242 (43.0) | 113 (27.9) | <.001 | 0.32 | 305 (46.2) | 116 (37.7) | .015 | 0.17 | 277 (36.1) | 61 (38.4) | .648 | 0.05 |
| Immunosuppression by ICD-10 code and/or self-report | 1043 (52.4) | 375 (43.0) | <.001 | 0.19 | 318 (56.5) | 157 (38.8) | <.001 | 0.36 | 380 (57.6) | 141 (45.8) | .001 | 0.24 | 345 (44.9) | 77 (48.4) | .47 | 0.07 |
| Influenza vaccination habite | ||||||||||||||||
| Never/rarely | 106 (5.3) | 543 (62.3) | <.001 | 1.69 | 45 (8.0) | 246 (60.7) | <.001 | 1.54 | 41 (6.2) | 198 (64.3) | <.001 | 1.61 | 20 (2.6) | 99 (62.3) | <.001 | 1.84 |
| Sometimes | 91 (4.6) | 88 (10.1) | 38 (6.7) | 54 (13.3) | 36 (5.5) | 22 (7.1) | 17 (2.2) | 12 (7.5) | ||||||||
| Always/almost always | 1794 (90.1) | 241 (27.6) | 480 (85.3) | 105 (25.9) | 583 (88.3) | 88 (28.6) | 731 (95.2) | 48 (30.2) | ||||||||
| Vaccination habit score (0–2), mean (SD) | 1.85 (0.49) | 0.65 (0.88) | <.001 | 1.68 | 1.77 | 0.65 | <.001 | 1.52 | 1.82 | 0.64 | <.001 | 1.61 | 1.93 | 0.68 | <.001 | 1.81 |
| Admission characteristics | ||||||||||||||||
| Days from illness onset to admission, mean (SD) | 2.87 (2.35) | 2.93 (2.37) | .513 | 0.03 | 2.96 (2.35) | 2.90 (2.35) | .656 | 0.03 | 2.98 (2.37) | 2.97 (2.41) | .97 | 0.00 | 2.71 (2.33) | 2.95 (2.37) | .236 | 0.10 |
| Admitted to tertiary care hospital | 1055 (53.0) | 501 (57.5) | .03 | 0.09 | 363 (64.5) | 243 (60.0) | .176 | 0.09 | 366 (55.5) | 179 (58.1) | .479 | 0.05 | 326 (42.4) | 79 (49.7) | .113 | 0.15 |
| Presented with influenza-like illnessf | 852 (42.8) | 416 (47.7) | .017 | 0.10 | 280 (49.7) | 234 (57.8) | .016 | 0.16 | 280 (42.4) | 135 (43.8) | .732 | 0.03 | 292 (38.0) | 47 (29.6) | .054 | 0.18 |
| Admitted to intensive care unit | 219 (11.0) | 119 (13.7) | .049 | 0.08 | 62 (11.0) | 54 (13.3) | .319 | 0.07 | 73 (11.1) | 42 (13.7) | .287 | 0.08 | 84 (11.0) | 23 (14.6) | .251 | 0.11 |
| Length of hospital stay, d, mean (SD) | 4.76 (4.30) | 4.73 (4.70) | .867 | 0.01 | 4.65 (4.77) | 4.60 (5.43) | .867 | 0.01 | 4.71 (4.40) | 4.61 (3.65) | .715 | 0.03 | 4.88 (3.83) | 5.30 (4.51) | .218 | 0.10 |
| Died in hospital | 26 (1.3) | 7 (0.8) | .332 | 0.05 | 4 (0.7) | 1 (0.2) | .591 | 0.07 | 7 (1.1) | 4 (1.3) | 1 | 0.02 | 15 (2.0) | 2 (1.3) | .787 | 0.06 |
Data are presented as No. (%) unless otherwise indicated.
Abbreviations: ACIP, Advisory Committee on Immunization Practices; ICD-10, International Classification of Diseases, 10th Edition; SD, standard deviation.
aVaccination defined as documented and/or plausible self-report.
b P value for test of difference across case and control groups based on χ 2 statistic for categorical variables, t test for difference of means of normally distributed continuous variables, and nonparametric log-rank test for nonnormally distributed continuous variables.
cStandardized absolute mean differences >0.10 shown in bold; standardized differences ≤0.10 are generally considered negligible differences between groups.
dDerived from ICD-10 codes associated with inpatient and outpatient medical encounters in the year prior to admission.
eDefined by patient self-report during enrollment interview.
fInfluenza-like illness defined as self-reported subjective fever/feverishness plus cough or sore throat.