Table 1.
Characteristics of the Omicron cohort and the Delta cohort before and after propensity matching. Omicron cohort – children under age 5 years who first contracted SARS-CoV-2 infection between 12/26/2021–1/6/2022 when Omicron was predominant and accounted for over 92% of all variants circulating in the US. Delta cohort – children under age 5 years who first contracted SARS-CoV-2 infection between 9/1/2021–11/15/2021 when Delta was predominant and accounted for 99% of all variants circulating in the US. Race and ethnicity as recorded in the TriNetX EHR database were included because they have been associated with both infection risk and severe outcomes of SARS-CoV-2 infections. P-value – significance between the two cohorts based on two-tailed two-proportion z-test conducted within the TriNetX Network.
| Before Matching | After Matching | |||||
|---|---|---|---|---|---|---|
| Omicron cohort | Delta Cohort | P-value | Omicron cohort | Delta Cohort | P-value | |
| Total number of infected children under 5 | 7,201 | 63,203 | 7,198 | 7,198 | ||
| Age (years, mean±SD) | 1.49 ± 1.42 | 1.73 ± 1.41 | < .001 | 1.49 ± 1.42 | 1.48 ± 1.42 | 0.76 |
| Sex (%) | ||||||
| Female | 47.4 | 46.4 | 0.12 | 47.4 | 47.6 | 0.74 |
| Male | 52.6 | 53.6 | 0.12 | 52.6 | 52.3 | 0.74 |
| Ethnicity (%) | ||||||
| Hispanic/Latinx | 13.7 | 15.5 | < .001 | 13.7 | 13.8 | 0.81 |
| Not Hispanic/Latinx | 33.0 | 53.2 | < .001 | 33.0 | 33.6 | 0.51 |
| Unknown | 53.3 | 31.3 | < .001 | 53.3 | 52.6 | 0.43 |
| Race (%) | ||||||
| African American/Black | 26.1 | 20.0 | < .001 | 26.1 | 26.8 | 0.34 |
| Asian | 2.4 | 2.5 | 0.59 | 2.4 | 2.5 | 0.91 |
| White | 44.0 | 49.6 | < .001 | 44.0 | 43.4 | 0.49 |
| Unknown | 27.0 | 27.4 | 0.49 | 27.0 | 26.9 | 0.91 |
| Adverse Social determinants of health (%) | 1.4 | 2.6 | < .001 | 1.4 | 1.4 | 0.72 |
| Comorbidities (%) | ||||||
| Cancer | 1.7 | 2.4 | < .001 | 1.7 | 1.5 | 0.29 |
| Congenital heart diseases | 1.8 | 2.9 | < .001 | 1.8 | 1.6 | 0.31 |
| Type 1 diabetes | 0 | 0.05 | 0.06 | 0 | 0 | - |
| Type 2 diabetes | 0 | 0.03 | 0.14 | 0 | 0 | - |
| Asthma | 1.7 | 3.7 | < .001 | 1.7 | 1.5 | 0.32 |
| Blood Disorders including Anemia, Neutropenia, Coagulation Disorders | 2.4 | 4.6 | < .001 | 2.4 | 2.3 | 0.58 |
| BMI > 95th Percentile for Age | 0.5 | 1.1 | < .001 | 0.5 | 0.4 | 0.31 |
| BMI between 85th-95th Percentile for Age | 0.5 | 1.0 | < .001 | 0.5 | 0.5 | 0.91 |
| BMI < 5th Percentile for Age | 0.2 | 0.5 | < .001 | 0.2 | 0.2 | 0.86 |
| Influenza and Pneumonia | 3.4 | 5.0 | < .001 | 3.4 | 3.2 | 0.40 |
| Common cold | 2.2 | 3.8 | < .001 | 2.2 | 1.8 | 0.08 |
| Autistic Disorder | 0.3 | 0.7 | < .001 | 0.3 | 0.3 | 0.66 |
| COVID-19 therapeutics (%) | ||||||
| Dexamethasone | 14.2 | 13.5 | < .001 | 14.2 | 14.2 | 0.98 |
| Hydrocortisone | 6.1 | 8.2 | < .001 | 6.1 | 5.6 | 0.24 |
| Ibuprofen | 25.6 | 26.2 | 0.27 | 25.5 | 25.7 | 0.79 |
| Prednisone | 0.2 | 0.3 | 0.12 | 0.2 | 0.1 | 0.53 |
| Methylprednisolone | 6.8 | 4.3 | < .001 | 6.8 | 6.4 | 0.33 |
| Prednisolone | 5.7 | 6.2 | 0.09 | 5.7 | 5.1 | 0.13 |
| Naproxen | 0.0 | 0.03 | 0.13 | 0.0 | 0.0 | - |
| Tocilizumab | 0.0 | 0.02 | 0.24 | 0.0 | 0.0 | - |