Multisystem Inflammatory Syndrome in Children—United States, February 2020–July 2021

Abstract

Background

Multisystem inflammatory syndrome in children (MIS-C) is a severe hyperinflammatory condition in persons aged <21 years associated with antecedent SARS-CoV-2 infection. Our objective was to describe MIS-C cases reported to CDC’s national surveillance since the COVID-19 pandemic began.

Methods

We included patients meeting the MIS-C case definition with onset date from February 19, 2020 through July 31, 2021, using CDC’s MIS-C case report form, which collects information on demographics, clinical presentation, and laboratory results. Trends over time across 3 MIS-C pandemic waves were assessed using Cochran-Armitage test for categorical and Jonckheere-Terpstra test for continuous variables.

Results

Of 4,901 reported cases, 4,470 met inclusion criteria. Median patient age increased over time (P<0.001), with a median of 9 years (interquartile range, 5–13 years) during the most recent (third) wave. Male predominance also increased (62% in third wave, P<0.001). A significant (P<0.001) increase in severe hematologic and gastrointestinal involvement was observed across the study period. Frequency of several cardiovascular complications (i.e., cardiac dysfunction, myocarditis, and shock/ vasopressor receipt) and renal failure declined (P<0.001). Provision of critical care including mechanical ventilation (P<0.001) and extracorporeal membrane oxygenation (ECMO; P=0.046) decreased, as did duration of hospitalization and mortality (each P<0.001).

Conclusions

Over the first 3 pandemic waves of MIS-C in the United States, cardiovascular complications and clinical outcomes including length of hospitalization, receipt of ECMO, and death decreased over time. These data serve as a baseline for monitoring future trends associated with SARS-CoV-2 B.1.617.2 (Delta) or other variants and increased COVID-19 vaccination among children.