Table. Characteristics of the Omicron Cohort and the Delta Cohort Before and After Propensity Matchinga.
| Characteristic | Before matching | After matching | ||||
|---|---|---|---|---|---|---|
| Cohort, No. (%) | SMD | Cohort, No. (%) | SMD | |||
| Omicron | Delta | Omicron | Delta | |||
| Total No. of infected children <5 y | 22 772 | 66 692 | 22 769 | 22 769 | ||
| Age, mean (SD), y | 1.5 (1.42) | 1.7 (1.39) | 0.14 | 1.5 (1.42) | 1.5 (1.42) | 0.005 |
| Sex | ||||||
| Female | 10 780 (47.3) | 30 978 (46.4) | 0.02 | 10 780 (47.3) | 10 802 (47.4) | 0.002 |
| Male | 11 987 (52.6) | 35 689 (53.5) | 0.02 | 11 984 (52.6) | 11 958 (52.5) | 0.002 |
| Ethnicity | ||||||
| Hispanic/Latinx | 2972 (13.1) | 10 562 (15.8) | 0.08 | 2972 (13.1) | 2977 (13.1) | <.001 |
| Not Hispanic/Latinx | 9025 (39.6) | 36 136 (54.2) | 0.29 | 9025 (39.6) | 9080 (39.9) | 0.005 |
| Unknown | 10 775 (47.3) | 19 994 (30.0) | 0.36 | 10 772 (47.3) | 10 712 (47.0) | 0.005 |
| Race | ||||||
| Asian | 518 (2.3) | 1595 (2.4) | 0.01 | 518 (2.3) | 536 (2.4) | 0.005 |
| Black | 4388(19.3) | 12 483 (18.7) | 0.01 | 4387 (19.3) | 4313 (18.9) | 0.008 |
| White | 10 826 (47.5) | 31 291 (46.9) | 0.01 | 10 824 (47.5) | 10 837 (47.6) | 0.001 |
| Unknown | 6935 (30.5) | 21 019 (31.5) | 0.02 | 6935 (30.5) | 6975 (30.6) | 0.004 |
| Adverse social determinants of health | 352 (1.5) | 1750 (2.6) | 0.08 | 352 (1.5) | 311 (1.4) | 0.02 |
| Comorbidities | ||||||
| Cancer | 434 (1.9) | 1641 (2.5) | 0.04 | 432 (1.9) | 420 (1.8) | 0.004 |
| Congenital heart diseases | 520 (2.3) | 1930 (2.9) | 0.04 | 520 (2.3) | 511 (2.2) | 0.003 |
| Diabetes | ||||||
| Type 1 | 10 (0.04) | 34 (0.05) | 0.003 | 10 (0.04) | 10 (0.04) | <.001 |
| Type 2 | 11 (0.05) | 34 (0.05) | 0.001 | 10 (0.05) | 10 (0.04) | <.001 |
| Asthma | 474 (2.1) | 2385 (3.6) | 0.09 | 474 (2.1) | 438 (1.9) | 0.01 |
| Blood disorders including anemia, neutropenia, coagulation disorders | 664 (2.9) | 2999 (4.5) | 0.08 | 664 (2.9) | 666 (2.9) | <.001 |
| BMI, percentile for age | ||||||
| ≥95th | 118 (0.5) | 718 (1.1) | 0.06 | 118 (0.5) | 106 (0.5) | 0.008 |
| Between 85th-95th | 106 (0.5) | 602 (0.9) | 0.04 | 106 (0.5) | 91 (0.4) | 0.01 |
| <5th | 66 (0.3) | 326 (0.5) | 0.03 | 66 (0.3) | 66 (0.3) | <.001 |
| Autistic disorder | 89 (0.4) | 456 (0.7) | 0.04 | 89 (0.4) | 93 (0.4) | 0.003 |
| Attention-deficit hyperactivity disorders | 30 (0.1) | 116 (0.2) | 0.01 | 30 (0.1) | 28 (0.1) | 0.003 |
Abbreviations: BMI, body mass index; SMD, standardized mean difference.
a
Cohorts were propensity-score matched 1:1 using greedy nearest-neighbor matching with a caliper of 0.25 × SD.