Belay ED, Abrams J, Oster ME, et al. - Two peaks were identified in this cross-sectional study of a large cohort of patients with the multisystem inflammatory syndrome in children (MIS-C) that followed COVID-19 peaks by 2 to 5 weeks.

• The geographic and temporal link between MIS-C and the COVID-19 pandemic suggested that MIS-C was caused by delayed immunologic responses to SARS-CoV-2 infection.

• The clinical manifestations differed according to age and the presence or absence of the previous COVID-19.

• In total, 1,733 patients with MIS-C were identified; 994 (57.6%) being male and 1,117 (71.3%) being Hispanic or non-Hispanic Black.

• It was noted that 53% (n = 931) to 67% (n = 1,153) of patients reported gastrointestinal symptoms, rash, and conjunctival hyperemia.

• There were 937 patients (54%) who had hypotension or shock, and 1,009 (58.2%) were admitted to intensive care.

• Four hundred eighty-four patients (31.0%) had cardiac dysfunction, 365 (23.4%) had pericardial effusion, 300 (17.3%) had myocarditis, and 258 (16.5%) had coronary artery dilatation or aneurysms.

• Although 171 patients (38.4%) had hypotension or shock and 197 (44.3%) were admitted for intensive care, children aged 0 to 4 years had the lowest proportion of severe manifestations.

• Myocarditis, pneumonia, acute respiratory distress syndrome, and polymerase chain reaction positivity were found in the highest proportions in patients aged 18 to 20 years.

• These older adolescents also had the highest proportion of COVID-19–like illness (63%) in the previous year.

• Nationally, the first 2 MIS-C peaks occurred 2 to 5 weeks after the COVID-19 peaks.

• The cumulative MIS-C incidence per 100,000 persons younger than 21 years was 2.1, ranging from 0.2 to 6.3 depending on the state.

• A total of 24 patients (1.4%) died.