Table 1. Description of Cohort, Cases, and Controls.
| Characteristic | Entire Cohort (N = 495 193) | Nested Case-Control | |
|---|---|---|---|
| Cases (n = 193)a | Controls (n = 751) | ||
| Female, No. (%) | 241 551 (48.8)b | 87 (45.1) | 335 (44.6) |
| Pediatric Medical Complexity Algorithm, No. (%)c | |||
| Nonchronic | 423 529 (85.5) | 140 (72.5) | 560 (74.6) |
| Noncomplex chronic | 52 941 (10.7) | 38 (19.7) | 145 (19.3) |
| Complex chronic | 18 723 (3.8) | 15 (7.8) | 46 (6.1) |
| Estimated cumulative vaccine antigen exposure from birth through 23 mo, No. of antigens | |||
| Mean (SD) | 254.6 (53.6) | 240.6 (48.3) | 242.9 (51.1) |
| Median (range) | 266 (0-428) | 236 (5-323) | 235 (0-399) |
| Estimated maximum single-day antigen exposure from birth through 23 mo, No. of antigens | |||
| Mean (SD) | 102.4 (20.4) | 101.0 (18.4) | 100.5 (18.9) |
| Median (range) | 107 (0-162) | 104 (5-136) | 104 (0-131) |
| Age as of case date, mo | |||
| Mean (SD) | 32.5 (6.3) | 32.5 (6.2) | |
| Median (range) | 32.0 (24.0-47.0) | 31.0 (24.0-47.0) | |
| Outpatient visits from birth through 23 mo, No. | |||
| Mean (SD) | 16.6 (8.1) | 19.6 (14.0) | 17.1 (7.7) |
| Median (range) | 15.0 (2.0-350.0) | 17.0 (6.0-131.0) | 15.0 (5.0-67.0) |
a
Of the 193 confirmed cases, 85 (44.0%) were from an inpatient setting and 108 (56.0%) were from an emergency department setting.
b
Three people were missing data on sex.
c
The Pediatric Medical Complexity Algorithm was applied to diagnosis code data among cohort members from birth through 23 months. Children classified as having complex chronic disease had 1 or more diagnoses for a progressive medical condition, 1 or more diagnoses for a malignancy, or 2 or more diagnoses per body system for at least 2 body systems. Children classified as having noncomplex chronic disease had 2 or more diagnoses within 1 body system. Children classified as nonchronic did not fall into either of these previous 2 categories.