IMPORTANCE Multiple inflammatory syndrome in children (MIS-C) occurs in association with the COVID-19 pandemic. OBJECTIVE To describe the clinical characteristics and geographic and temporal distribution of the largest cohort of patients with MIS-C in the United States to date. DESIGN, SETTING, AND PARTICIPANTS Cross-sectional analysis was conducted on clinical and laboratory data collected from patients with MIS-C. The analysis included patients with illness onset from March 2020 to January 2021 and met MIS-C case definition.MAIN OUTCOMES AND MEASURES Geographic and temporal distribution of MIS-C was compared with that of COVID-19 nationally, by region, and level of urbanicity by county. Clinical and laboratory findings and changes over time were described by age group and by presence or absence of preceding COVID-19.RESULTS A total of 1733 patients with MIS-C were identified; 994 (57.6%) were male and 1117 (71.3%) were Hispanic or non-Hispanic Black. Gastrointestinal symptoms, rash, and conjunctival hyperemia were reported by 53% (n = 931) to 67% (n = 1153) of patients. A total of 937 patients (54%) had hypotension or shock, and 1009 (58.2%) were admitted for intensive care. Cardiac dysfunction was reported in 484 patients (31.0%), pericardial effusion in 365 (23.4%), myocarditis in 300 (17.3%), and coronary artery dilatation or aneurysms in 258 (16.5%). Patients aged 0 to 4 years had the lowest proportion of severe manifestations, although 171 patients (38.4%) had hypotension or shock and 197 (44.3%) were admitted for intensive care. Patients aged 18 to 20 years had the highest proportions with myocarditis (17 [30.9%]), pneumonia (20 [36.4%]), acute respiratory distress syndrome (10 [18.2%]), and polymerase chain reaction positivity (39 [70.9%]). These older adolescents also had the highest proportion reporting preceding COVID-19-like illness (63%). Nationally, the first 2 MIS-C peaks followed the COVID-19 peaks by 2 to 5 weeks. The cumulative MIS-C incidence per 100 000 persons younger than 21 years was 2.1 and varied from 0.2 to 6.3 by state. Twenty-four patients (1.4%) died. CONCLUSIONS AND RELEVANCEIn this cross-sectional study of a large cohort of patients with MIS-C, 2 peaks that followed COVID-19 peaks by 2 to 5 weeks were identified. The geographic and temporal association of MIS-C with the COVID-19 pandemic suggested that MIS-C resulted from delayed immunologic responses to SARS-CoV-2 infection. The clinical manifestations varied by age and by presence or absence of preceding COVID-19.

Background Late sequelae of COVID-19 have been reported; however, few studies have investigated the time-course or incidence of late new COVID-19-related health conditions (post-COVID conditions) after COVID-19 diagnosis. Studies distinguishing post-COVID conditions from late conditions caused by other etiologies are lacking. Using data from a large administrative all-payer database, we assessed the type, association, and timing of post-COVID conditions following COVID-19 diagnosis. Methods Using the Premier Healthcare Database Special COVID-19 Release (PHD-SR) (release date, October 20, 2020) data, during March–June 2020, 27,589 inpatients and 46,857 outpatients diagnosed with COVID-19 (case-patients) were 1:1 matched with patients without COVID-19 through the 4-month follow-up period (control-patients) by using propensity score matching. In this matched-cohort study, adjusted odds ratios were calculated to assess for late conditions that were more common in case-patients compared with control-patients. Incidence proportion was calculated for conditions that were more common in case-patients than control-patients during 31–120 days following a COVID-19 encounter. Results During 31–120 days after an initial COVID-19 inpatient hospitalization, 7.0% of adults experienced at least one of five post-COVID conditions. Among adult outpatients with COVID-19, 7.7% experienced at least one of ten post-COVID conditions. During 31–60 days after an initial outpatient encounter, adults with COVID-19 were 2.8 times as likely to experience acute pulmonary embolism as outpatient control-patients and were also more likely to experience a range of conditions affecting multiple body systems (e.g. nonspecific chest pain, fatigue, headache, and respiratory, nervous, circulatory, and gastrointestinal system symptoms) than outpatient control-patients. Children with COVID-19 were not more likely to experience late conditions than children without COVID-19. Conclusions These findings add to the evidence of late health conditions possibly related to COVID-19 in adults following COVID-19 diagnosis and can inform health care practice and resource planning for follow-up COVID-19 care.

Background: Multisystem inflammatory syndrome in children (MIS-C), temporally associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been identified in infants <12 months old. Clinical characteristics and follow-up data of MIS-C in infants have not been well described. We sought to describe the clinical course, laboratory findings, therapeutics and outcomes among infants diagnosed with MIS-C. Methods: Infants of age <12 months with MIS-C were identified by reports to the CDC's MIS-C national surveillance system. Data were obtained on clinical signs and symptoms, complications, treatment, laboratory and imaging findings, and diagnostic SARS-CoV-2 testing. Jurisdictions that reported 2 or more infants were approached to participate in evaluation of outcomes of MIS-C. Results: Eighty-five infants with MIS-C were identified and 83 (97.6%) tested positive for SARS-CoV-2 infection; median age was 7.7 months. Rash (62.4%), diarrhea (55.3%) and vomiting (55.3%) were the most common signs and symptoms reported. Other clinical findings included hypotension (21.2%), pneumonia (21.2%) and coronary artery dilatation or aneurysm (13.9%). Laboratory abnormalities included elevated C-reactive protein, ferritin, d-dimer and fibrinogen. Twenty-three infants had follow-up data; 3 of the 14 patients who received a follow-up echocardiogram had cardiac abnormalities during or after hospitalization. Nine infants had elevated inflammatory markers up to 98 days postdischarge. One infant (1.2%) died after experiencing multisystem organ failure secondary to MIS-C. Conclusions: Infants appear to have a milder course of MIS-C than older children with resolution of their illness after hospital discharge. The full clinical picture of MIS-C across the pediatric age spectrum is evolving.

Idiopathic intussusception is a common cause of bowel obstruction in infants, presenting as refractory abdominal pain or mass, vomiting, lethargy, and currant jelly stool. Coronavirus disease 2019 is not well characterized in children, especially infants, but symptoms in children have included nausea, vomiting, diarrhea, and abdominal pain. From January to July 2020, intussusception was reported in 5 infants 4–10 months of age who had laboratory-confirmed SARS-CoV-2 infection. All 5 infants presented with currant jelly stool and at least 1 other abdominal symptom, and none presented with respiratory symptoms. Four infants recovered but the fifth infant progressed to a critical illness and death. While an association between SARS-CoV-2 infection and intussusception has not been established, infants with symptoms consistent with intussusception may warrant testing for viral pathogens, including SARS-CoV-2, especially if presenting to healthcare with a history of SARS-CoV-2 exposure or with signs and symptoms of COVID-19. More investigation is needed to determine whether intussusception is part of the clinical spectrum of COVID-19 in infants or a coincidental finding among infants with SARS-CoV-2 infection.