J Korean Med Sci.  2023 Jul;38(30):e225. 10.3346/jkms.2023.38.e225.

Change in Severity and Clinical Manifestation of MIS-C Over SARSCoV-2 Variant Outbreaks in Korea

• Choe YJ
• Choi EH
• Choi JW
• Eun BW
• Eun LY
• Kim YJ
• Kim YH
• Kim YA
• Kim YK
• Kwak JH
• Lee H
• Park JD
• Jung YH
• Gwack J
• Lee S
• on behalf of MIS-C Surveillance Group

• KMID: 2544949
• DOI: http://doi.org/10.3346/jkms.2023.38.e225

Abstract

Background
There is difference in the incidence of multi-system inflammatory syndrome in children (MIS-C) in patients with different variants of severe acute respiratory syndrome coronavirus 2, however, little is known about the epidemiology in Asian countries. We investigated and compared the epidemiology of the MIS-C during omicron-dominant period with that of previous periods in South Korea.
Methods
We obtained clinical, epidemiological and laboratory data on MIS-C cases from national MIS-C surveillance in South Korea. We defined pre-delta period as January 2020–May 2021; delta period as June 2021–December 2021; and omicron period as January 2022–April 2022. We describe the clinical characteristics and outcomes of MIS-C patients by period.
Results
A total of 91 cases were assessed to be MIS-C cases. Number of MIS-C cases have increased from six cases during pre-delta period to 66 cases during omicron period, while the incidence rate (the number of MIS-C cases per 100,000 cases of reported coronavirus disease 2019) has decreased from 38.5 cases per 100,000 (95% confidence interval [CI], 14.1–83.9) during pre-delta period to 1.6 cases per 100,000 (95% CI, 1.2–2.0) during omicron periods. During pre-delta period, 66.7% and 100% had hypotension and gastrointestinal involvement, respectively; while during omicron period, 12.1% and 6.1% had such clinical manifestations. Fifty percent of pre-delta MIS-C patients were taken intensive care unit (ICU) cares, while 10.6% of patients during omicron periods were in ICUs.
Conclusion
Omicron period were associated with less severe clinical manifestation compared to pre-delta and delta periods. Although incidence rate of MIS-C was lower for the omicron period than pre-delta and delta periods, number of patients reported with MIS-C may pose a substantial clinical burden.

Keyword

MIS-C; COVID-19; SARS-CoV-2

Figure

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  Fig. 1 National MIS-C surveillance scheme, South Korea, 2020–2022.MIS-C = multi-system inflammatory syndrome in children, RT-PCR = reverse transcriptase polymerase chain reaction, PRNT = plaque reduction neutralization test, ELISA = enzyme-linked immunosorbent assay.

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  Fig. 2 Geographic distribution of institutions participated in the surveillance.

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  Fig. 3 Temporal trend of monthly putative SARS-CoV-2 exposures in MIS-C cases and their MIS-C occurrence (left axis), and total number of COVID-19 cases in 0–19 years (right axis, in log-scale).SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2, MIS-C = multi-system inflammatory syndrome in children, COVID-19 = coronavirus disease 2019.

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