Table 1.
Distribution of epidemiological characteristics of the study population in September 2021–December 2021 (Delta period) and January 2022–April 2022 (Omicron period)
| Variable | Categories | Study period | |||
|---|---|---|---|---|---|
| Total | Delta period | Omicron period | P-value | ||
| n(%) | n(%) | n(%) | |||
| Children tested | 1312 | 693 | 619 | ||
| Median age (IQR) | 84 (22.8–144) | 84 (20.8–144) | 84 (24–144) | 0.720 | |
| Seropositive | 506/1312 (38.6) | 206/693 (29.7) | 300/619 (48.5) | <0.0001 | |
| Gender | Female | 245/610 (40.2) | 101/308 (32.8) | 144/302 (47.7) | <0.001 |
| Male | 261/702 (37.2) | 105/385 (27.3) | 156/317 (49.2) | <0.001 | |
| P-value | 0.293 | 0.135 | 0.764 | ||
| Age group (years) | 0–1 years | 80/251 (31.9) | 45/144 (31.3) | 35/107 (32.7) | 0.914 |
| 1–4 years | 91/247 (36.8) | 37/123 (30.1) | 54/124 (43.6) | 0.039 | |
| 4–6 years | 52/132 (39.4) | 16/65 (24.6) | 36/67 (53.7) | 0.001 | |
| 6–12 years | 159/382 (41.6) | 55/198 (27.8) | 104/184 (56.5) | <0.001 | |
| 12–16 years | 124/300 (41.3) | 53/163 (32.5) | 71/137 (51.8) | 0.001 | |
| P-value | 0.109 | 0.746 | 0.001 | ||
| Department | Hospitalised | 351/914 (38.4) | 160/528 (30.3) | 191/386 (49.5) | <0.001 |
| Non-hospitalised | 155/398 (38.9) | 46/165 (27.9) | 109/233 (46.8) | <0.001 | |
| P-value | 0.902 | 0.619 | 0.570 | ||
| Origin | Greek | 377/1000 (37.7) | 161/550 (29.3) | 216/450 (48) | <0.001 |
| non-Greek | 129/312 (41.4) | 45/143 (31.5) | 84/169 (49.7) | 0.002 | |
| P-value | 0.276 | 0.682 | 0.774 | ||
IQR: interquartile range.
The categorical data were tested with the X2 test. The comparison of median age was tested with Wilcoxon rank sum test. Statistically significant (P-value <0.05) differences are marked in bold.