• Young June Choe, Eun Hwa Choi, Jong Woon Choi, Byung Wook Eun, Lucy Youngmin Eun, Yae-Jean Kim, Yeo Hyang Kim, Young A Kim, Yun-Kyung Kim, Ji Hee Kwak, Hyukmin Lee, June Dong Park, Yeon Haw Jung, Jin Gwack, Sangwon Lee, and MIS-C Surveillance Group.
• Department of Pediatrics, Korea University Anam Hospital, Seoul, Korea.
• J. Korean Med. Sci. 2023 Jul 31; 38 (30): e225e225.

BackgroundThere 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.MethodsWe 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.ResultsA 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.ConclusionOmicron 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.© 2023 The Korean Academy of Medical Sciences.

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