Table 1.
MIS-C cases (n = 152), SARS-CoV-2 infections, MIS-C incidence and rate between MIS-C cases and SARS-CoV-2 infections (from − 30 days w.r.t. the MIS-C interval) by SARS-CoV-2 variant. Population references (by group) for incidences are constant throughout all variants
| Incidences per variants | p-val | |||||||
|---|---|---|---|---|---|---|---|---|
| Age group/sex | Whole study period | Wuhan period (pre-Jul 1) | Wuhan period (post-Jul 1) | Alpha period | Delta period | Omicron period | ||
| MIS-C cases, n (%) | Total | 152 (100) | 16 (100) | 57 (100) | 5 (100) | 44 (100) | 30 (100) | - |
| 0–4 | 41 (27.0) | 6 (37.5) | 16 (28.1) | 3 (60.0) | 9 (20.4) | 7 (23.3) | - | |
| 5–11 | 74 (48.7) | 6 (37.5) | 25 (43.8) | 1 (20.0) | 27 (61.4) | 15 (50.0) | - | |
| 12–17 | 37 (24.3) | 4 (25.0) | 16 (28.1) | 1 (20.0) | 8 (18.2) | 8 (23.7) | - | |
| Female | 57 (37.5) | 6 (37.5) | 21 (36.8) | 4 (80.0) | 18 (40.9) | 8 (23.7) | - | |
| Male | 95 (62.5) | 10 (62.5) | 36 (63.2) | 1 (20.0) | 26 (59.1) | 22 (73.3) | - | |
| SARS-CoV-2 infections | Total | 555,848 (100) | 654 (100) | 78,158 (100) | 28,812 (100) | 81,814 (100) | 366,410 (100) | - |
| 0–4 | 89,883 (16.2) | 173 (26.5) | 12,674 (16.2) | 4226 (14.7) | 11,388 (13.9) | 61,422 (16.8) | - | |
| 5–11 | 242,430 (40.2) | 189 (28.9) | 28,905 (46.8) | 11,019 (47.1) | 35,934 (42.2) | 166,383 (37.8) | - | |
| 12–17 | 223,535 (43.6) | 292 (44.6) | 36,579 (37.0) | 13,567 (38.2) | 34,492 (43.9) | 138,605 (45.4) | - | |
| Female | 272,806 (49.1) | 339 (51.8) | 38,355 (49.1) | 13,877 (48.2) | 41,175 (50.3) | 179,060 (48.9) | - | |
| Male | 283,042 (50.9) | 315 (48.2) | 39,803 (50.9) | 14,935 (51.8) | 40,639 (49.7) | 187,350 (51.1) | - | |
| MIS-C monthly incidence (× 106) | Total | 4.1 | 3.6 | 5.0 | 0.8 | 4.9 | 4.6 | 0.68a |
| 0–4 | 5.0 | 6.1 | 6.4 | 2.3 | 4.6 | 4.8 | 0.85a | |
| 5–11 | 4.9 | 3.3 | 5.5 | 0.4 | 7.5 | 5.7 | 0.28a | |
| 12–17 | 2.6 | 2.4 | 3.7 | 0.4 | 2.4 | 3.2 | 0.7a | |
| Female | 3.1 | 2.8 | 3.8 | 1.4 | 4.1 | 2.5 | 0.6a | |
| Male | 4.9 | 4.3 | 6.1 | 0.3 | 5.6 | 6.5 | 0.73a | |
| Rate between MIS-C cases and SARS-CoV-2 infections (× 106) | Total | 273 | 24,465S | 729 | 174 | 538 | 82 | < 0.001b |
| 0–4 | 456 | 34,682S | 1262 | 710 | 790 | 114 | < 0.001b | |
| 5–11 | 305 | 31,746S | 865 | 91 | 751 | 90 | < 0.001b | |
| 12–17 | 166 | 13,699S | 437 | 74 | 232 | 58 | < 0.001b | |
| Female | 209 | 17,699S | 548 | 288 | 437 | 45 | < 0.001b | |
| Male | 336 | 31,746S | 905 | 67 | 640 | 117 | < 0.001b | |
| Rate ratio (Omicron reference) | Total | - | * | 8.9 (5.7–13.8) | 2.1 (0.8–5.5) | 6.6 (4.1–10.4) | 1 | - |
| 0–4 | - | * | 11.1 (4.6–26.9) | 6.2 (1.6–24.1) | 6.9 (2.6–18.6) | 1 | - | |
| 5–11 | - | * | 9.6 (5.1–18.2) | 1.0 (0.1–7.6) | 8.3 (4.4–15.7) | 1 | - | |
| 12–17 | - | * | 7.6 (3.2–17.7) | 1.3 (0.2–10.2) | 4.0 (1.5–10.7) | 1 | - | |
| Female | - | * | 12.2 (5.4–27.7) | 6.5 (1.9–21.4) | 9.8 (4.3–22.5) | 1 | - | |
| Male | - | * | 7.7 (4.5–13.1) | 0.6 (0.1–4.2) | 5.4 (3.1–9.6) | 1 | - | |
*Rate ratio is not included for the Wuhan period before July 1, 2020, due to the lack of methods available for COVID-19 diagnosis elsewhere in Catalonia, Spain
aP-values come from two-sided z-tests (α = 0.05) excluding the Alpha period
bP-values come from two-sided z-tests (α = 0.05) excluding the Wuhan period (before July 1, 2020)
SThe values of the MIS-C rate in Wuhan before July 1, 2020, are unable to be compared with the values for other periods (Wuhan after July 1, 2020, Alpha, Delta, and Omicron) due to the lack of access to COVID-19 diagnosis in the former period. Therefore, the analysis comparing the rates across the variants does not include the period of Wuhan before July 1, 2020