Table. Study Population Characteristics (N = 24 261).
| Characteristic | No. (%) | |||||
|---|---|---|---|---|---|---|
| Wild-type BNT162b2 vaccination status | Case (n = 2337) | Control (n = 21 924) | Total (N = 24 261) | |||
| Unvaccinated (n = 22 804) | Received 2 doses (n = 826) | Received 3 doses (n = 631) | ||||
| Unvaccinated | 2261 (96.7) | 20 543 (93.7) | 22 804 (9.4) | |||
| Received 2 vaccine doses | 41 (1.8) | 785 (3.6) | 826 (3.4) | |||
| Received 3 vaccine doses | 35 (1.5) | 596 (2.7) | 631 (2.6) | |||
| Case | 2261 (9.9) | 41 (5.0) | 35 (5.5) | 2337 (9.6) | ||
| Control | 20 543 (90.1) | 785 (95.0) | 596 (94.5) | 21 924 (90.4) | ||
| Age at time of encounter, y | ||||||
| <1 | 4488 (19.7) | 82 (9.9) | 17 (2.7) | 907 (38.8) | 3680 (16.8) | 4587 (18.9) |
| 1 | 4835 (21.2) | 154 (18.6) | 123 (19.5) | 559 (23.9) | 4553 (20.8) | 5112 (21.1) |
| 2 | 4505 (19.8) | 140 (16.9) | 180 (28.5) | 314 (13.4) | 4511 (20.6) | 4825 (19.9) |
| 3 | 4504 (19.8) | 195 (23.6) | 149 (23.6) | 284 (12.2) | 4564 (20.8) | 4848 (20.0) |
| 4 | 4472 (19.6) | 255 (30.9) | 162 (25.7) | 273 (11.7) | 4616 (21.1) | 4889 (20.2) |
| Sex | ||||||
| Female | 10 466 (45.9) | 397 (48.1) | 298 (47.2) | 1103 (47.2) | 10 058 (45.9) | 11 161 (46.0) |
| Male | 12 338 (54.1) | 429 (51.9) | 333 (52.8) | 1234 (52.8) | 11 866 (54.1) | 13 100 (54.0) |
| Self-reported race and ethnicity | ||||||
| African American or Black | 2035 (8.9) | 36 (4.4) | 34 (5.4) | 169 (7.2) | 1936 (8.8) | 2105 (8.7) |
| Asian or Pacific Islander | 2073 (9.1) | 191 (23.1) | 150 (23.8) | 268 (11.5) | 2146 (9.8) | 2414 (10.0) |
| Hispanic or Latinx | 12 929 (56.7) | 368 (44.6) | 239 (37.9) | 1325 (56.7) | 12 211 (55.7) | 13 536 (55.8) |
| White | 4464 (19.6) | 183 (22.2) | 184 (29.2) | 442 (18.9) | 4389 (20) | 4831 (19.9) |
| Other or unknowna | 1303 (5.7) | 48 (5.8) | 24 (3.8) | 133 (5.7) | 1242 (5.7) | 1375 (5.7) |
| Encounter type | ||||||
| Emergency department | 11 040 (48.4) | 357 (43.2) | 218 (34.5) | 1272 (54.4) | 10 343 (47.2) | 11 615 (47.9) |
| Urgent care | 6624 (29) | 254 (30.8) | 196 (31.1) | 457 (19.6) | 6617 (30.2) | 7074 (29.2) |
| In-person outpatient | 5140 (22.5) | 215 (26.0) | 217 (34.4) | 608 (26.0) | 4964 (22.6) | 5572 (23.0) |
| Pediatric risk scoreb | ||||||
| 0 | 10 672 (46.8) | 378 (45.8) | 293 (46.4) | 1121 (48) | 10 222 (46.6) | 11 343 (46.8) |
| 1 | 5160 (22.6) | 197 (23.8) | 159 (25.2) | 395 (16.9) | 5121 (23.4) | 5516 (22.7) |
| 2 | 4016 (17.6) | 133 (16.1) | 95 (15.1) | 491 (21.0) | 3753 (17.1) | 4244 (17.5) |
| 3 | 1444 (6.3) | 49 (5.9) | 34 (5.4) | 170 (7.3) | 1357 (6.2) | 1527 (6.3) |
| ≥4 | 1512 (6.6) | 69 (8.4) | 50 (7.9) | 160 (6.8) | 1471 (6.7) | 1631 (6.7) |
| Previous positive PCR test result for SARS-CoV-2 | ||||||
| 0 | 18 664 (81.8) | 656 (79.4) | 513 (81.3) | 2156 (92.3) | 17 677 (80.6) | 19 833 (81.7) |
| 1 | 4140 (18.2) | 170 (20.6) | 118 (18.7) | 181 (7.7) | 4247 (19.4) | 4428 (18.3) |
| Received flu vaccine in year prior to encounter | ||||||
| 0 | 12 142 (53.2) | 180 (21.8) | 81 (12.8) | 1166 (49.9) | 11 237 (51.3) | 12 403 (51.1) |
| 1 | 10 662 (46.8) | 646 (78.2) | 550 (87.2) | 1171 (50.1) | 10 687 (48.7) | 11 858 (48.9) |
Abbreviations: BNT162b2, Pfizer-BioNTech COVID-19 vaccine bivalent; PCR, polymerase chain reaction.
a
Race and ethnicity were reported by the participant’s parent or guardian and recorded in the health record. “Other” includes individuals who self-identified as American Indian or “multiple” or “other” race and ethnicity categories. Race and ethnicity were included as a confounder due to associations with vaccination and COVID-19 health care–seeking behavior and outcomes.
b
A summary measure of disease burden in which a higher score indicates higher comorbidity.