A Linkable, Polycarbonate Gut Microbiome-Distal Tumor Chip Platform for Interrogating Cancer Promoting Mechanisms.

Gut microbiome composition is tied to diseases ranging from arthritis to cancer to depression. However, mechanisms of action are poorly understood, limiting development of relevant therapeutics. Organ-on-chip platforms, which model minimal functional units of tissues and can tightly control communication between them, are ideal platforms to study these relationships. Many gut microbiome models are published to date but devices are typically fabricated using oxygen permeable polydimethylsiloxane, requiring interventions to support anaerobic bacteria. To address this challenge, a platform is developed where the chips are fabricated entirely from gas-impermeable polycarbonate without tapes or gaskets. These chips replicate polarized villus-like structures of the native tissue. Further, they enable co-cultures of commensal anaerobic bacteria Blautia coccoides on the surface of gut epithelia for two days within a standard incubator. Another complication of commonly used materials in organ-on-chip devices is high ad-/absorption, limiting applications in high-resolution microscopy and biomolecule interaction studies. For future communication studies between gut microbiota and distal tumors, an additional polycarbonate chip design is developed to support hydrogel-embedded tissue culture. These chips enable high-resolution microscopy with all relevant processing done on-chip. Designed for facile linking, this platform will make a variety of mechanistic studies possible.

Using unstructured crowd-sourced data to evaluate urban tolerance of terrestrial native animal species within a California Mega-City.

In response to biodiversity loss and biotic community homogenization in urbanized landscapes, there are increasing efforts to conserve and increase biodiversity within urban areas. Accordingly, around the world, previously extirpated species are (re)colonizing and otherwise infiltrating urban landscapes, while other species are disappearing from these landscapes. Tracking the occurrence of traditionally urban intolerant species and loss of traditionally urban tolerant species should be a management goal of urban areas, but we generally lack tools to study this phenomenon. To address this gap, we first used species' occurrences from iNaturalist, a large collaborative dataset of species observations, to calculate an urban association index (UAI) for 967 native animal species that occur in the city of Los Angeles. On average, the occurrence of native species was negatively associated with our composite measure of urban intensity, with the exception of snails and slugs, which instead occur more frequently in areas of increased urban intensity. Next, we assessed 8,348 0.25 x 0.25 mile grids across the City of Los Angeles to determine the average grid-level UAI scores (i.e., a summary of the UAIs present in a grid cell, which we term Community Urban Tolerance Index or CUTI). We found that areas of higher urban intensity host more urban tolerant species, but also that taxonomic groups differ in their aggregate tolerance of urban areas, and that spatial patterns of tolerance vary between groups. The framework established here has been designed to be iteratively reevaluated by city managers of Los Angeles in order to track the progress of initiatives to preserve and encourage urban biodiversity, but can be rescaled to sample different regions within the city or different cities altogether to provide a valuable tool for city managers globally.

Feasible diet and circadian interventions reduce in vivo progression of FLT3-ITD-positive acute myeloid leukemia.

BACKGROUND: Acute myeloid leukemia (AML) with an internal tandem duplication in the fms-like tyrosine kinase receptor 3 gene (FLT3-ITD) is associated with poor survival, and few studies have examined the impact of modifiable behaviors, such as nutrient quality and timing, in this subset of acute leukemia. METHODS: The influence of diet composition (low-sucrose and/or low-fat diets) and timing of diet were tested in tandem with anthracycline treatment in orthotopic xenograft mouse models. A pilot clinical study to test receptivity of pediatric leukemia patients to macronutrient matched foods was conducted. A role for the circadian protein, BMAL1 (brain and muscle ARNT-like 1), in effects of diet timing was studied by overexpression in FLT3-ITD-bearing AML cells. RESULTS: Reduced tumor burden in FLT3-ITD AML-bearing mice was observed with interventions utilizing low-sucrose and/or low-fat diets, or time-restricted feeding (TRF) compared to mice fed normal chow ad libitum. In a tasting study, macronutrient matched low-sucrose and low-fat meals were offered to pediatric acute leukemia patients who largely reported liking the meals. Expression of the circadian protein, BMAL1, was heightened with TRF and the low-sucrose diet. BMAL1 overexpression and treatment with a pharmacological inducer of BMAL1 was cytotoxic to FLT3-ITD AML cells. CONCLUSIONS: Mouse models for FLT3-ITD AML show that diet composition and timing slows progression of FLT3-ITD AML growth in vivo, potentially mediated by BMAL1. These interventions to enhance therapy efficacy show preliminary feasibility, as pediatric leukemia patients responded favorable to preparation of macronutrient matched meals.

Disproportionate Rates of COVID-19 Among Black Canadian Communities: Lessons from a Cross-Sectional Study in the First Year of the Pandemic.

BACKGROUND: Racialized communities, including Black Canadians, have disproportionately higher COVID-19 cases. We examined the extent to which SARS-CoV-2 infection has affected the Black Canadian community and the factors associated with the infection. METHODS: We conducted a cross-sectional survey in an area of Ontario (northwest Toronto/Peel Region) with a high proportion of Black residents along with 2 areas that have lower proportions of Black residents (Oakville and London, Ontario). SARS-CoV-2 IgG antibodies were determined using the EUROIMMUN assay. The study was conducted between August 15, 2020, and December 15, 2020. RESULTS: Among 387 evaluable subjects, the majority, 273 (70.5%), were enrolled from northwest Toronto and adjoining suburban areas of Peel, Ontario. The seropositivity values for Oakville and London were comparable (3.3% (2/60; 95% CI 0.4-11.5) and 3.9% (2/51; 95% CI 0.5-13.5), respectively). Relative to these areas, the seropositivity was higher for the northwest Toronto/Peel area at 12.1% (33/273), relative risk (RR) 3.35 (1.22-9.25). Persons 19 years of age or less had the highest seropositivity (10/50; 20.0%, 95% CI 10.3-33.7%), RR 2.27 (1.23-3.59). There was a trend for an interaction effect between race and location of residence as this relates to the relative risk of seropositivity. INTERPRETATION: During the early phases of the pandemic, the seropositivity within a COVID-19 high-prevalence zone was threefold greater than lower prevalence areas of Ontario. Black individuals were among those with the highest seroprevalence of SARS-CoV-2.

Association of cerebrospinal fluid parameters with treatment and complications among children with cerebrospinal fluid shunt infections: a multicenter study.

OBJECTIVE: Cerebrospinal fluid (CSF) white blood cell (WBC) count, neutrophil percentage, protein concentration, and glucose level are typically measured at diagnosis and serially during the treatment of CSF shunt infections. The objective of this retrospective cohort study was to describe the longitudinal profile of CSF parameters in children with CSF shunt infections and assess their association with treatment and outcome. METHODS: Participants were children treated at 11 tertiary pediatric hospitals in Canada and the United States for CSF shunt infection, from July 1, 2013, through June 30, 2019, with hardware removal, external ventricular drain placement, intravenous antibiotics, and subsequent permanent shunt reinsertion. The relationship between CSF parameters and a complicated course (a composite outcome representing children with at least one of the following: contiguous soft-tissue infection, worsening hydrocephalus, CSF leak, intracranial bleed, brain abscess, venous thrombosis, reinfection after insertion of the new shunt, other complication, ICU admission, or death) was analyzed. RESULTS: A total of 109 children (median age 2.8 years, 44% female) were included in this study. CSF pleocytosis, elevated protein, and hypoglycorrhachia had sensitivities of 69%, 47%, and 38% for the diagnosis of culture-confirmed CSF shunt infection, respectively. The longitudinal profile of the neutrophil percentage followed a monotonic trend, decreasing by 1.5% (95% CI 1.0%-2.0%, p < 0.0001) per day over the course of treatment. The initial WBC count differed significantly between pathogens (p = 0.011), but the proportion of neutrophils, protein concentration, and glucose level did not, and was lowest with Cutibacterium acnes. The duration of antibiotic treatment and the time to shunt reinsertion were longer in patients with a higher initial neutrophil percentage. Fifty-eight patients (53%) had one or more complications during their admission. A neutrophil percentage > 44% (Youden index) in the initial CSF sample was associated with a 1.8-fold (95% CI 1.2- to 2.8-fold) higher relative risk of a complicated course. In a random-intercept, random-slope linear mixed-effects model, the longitudinal neutrophil trajectory differed significantly between patients with and without complications (p = 0.030). CONCLUSIONS: A higher proportion of neutrophils in the CSF at diagnosis was associated with a complicated clinical course. Other CSF parameters were associated with treatment and outcome; however, wide variability in values may limit their clinical utility.

Neurological involvement in hospitalized children with SARS-CoV-2 infection: a multinational study.

BACKGROUND AND OBJECTIVES: Neurological involvement associated with SARS-CoV-2 infection is increasingly recognized. However, the specific characteristics and prevalence in pediatric patients remain unclear. The objective of this study was to describe the neurological involvement in a multinational cohort of hospitalized pediatric patients with SARS-CoV-2. METHODS: This was a multicenter observational study of children <18 years of age with confirmed SARS-CoV-2 infection or multisystemic inflammatory syndrome (MIS-C) and laboratory evidence of SARS-CoV-2 infection in children, admitted to 15 tertiary hospitals/healthcare centers in Canada, Costa Rica, and Iran February 2020-May 2021. Descriptive statistical analyses were performed and logistic regression was used to identify factors associated with neurological involvement. RESULTS: One-hundred forty-seven (21%) of 697 hospitalized children with SARS-CoV-2 infection had neurological signs/symptoms. Headache (n = 103), encephalopathy (n = 28), and seizures (n = 30) were the most reported. Neurological signs/symptoms were significantly associated with ICU admission (OR: 1.71, 95% CI: 1.15-2.55; p = 0.008), satisfaction of MIS-C criteria (OR: 3.71, 95% CI: 2.46-5.59; p < 0.001), fever during hospitalization (OR: 2.15, 95% CI: 1.46-3.15; p < 0.001), and gastrointestinal involvement (OR: 2.31, 95% CI: 1.58-3.40; p < 0.001). Non-headache neurological manifestations were significantly associated with ICU admission (OR: 1.92, 95% CI: 1.08-3.42; p = 0.026), underlying neurological disorders (OR: 2.98, 95% CI: 1.49-5.97, p = 0.002), and a history of fever prior to hospital admission (OR: 2.76, 95% CI: 1.58-4.82; p < 0.001). DISCUSSION: In this study, approximately 21% of hospitalized children with SARS-CoV-2 infection had neurological signs/symptoms. Future studies should focus on pathogenesis and long-term outcomes in these children.

Pseudohyperkalemia in horses with rhabdomyolysis reported by an enzymatic chemistry analyzer.

OBJECTIVE: To investigate pseudohyperkalemia occurring in horses experiencing rhabdomyolysis when serum chemistry profiles are run on an VetScan VS2 analyzer (Abaxis). ANIMALS: 18 horses with rhabdomyolysis (creatine kinase [CK] > 1,000 U/L). METHODS: In 3 horses with serum CK activities > 5,800 U/L and persistent serum potassium concentrations of > 8.5 mmol/L (VetScan VS2), potassium concentrations were reevaluated with either i-STAT Alinity Base Station (Abbott), Catalyst (Idexx), or Cobas c501 (Roche) ion-specific analyzers. Paired serum samples from 15 additional horses (median serum CK activity, 7,601 U/L; range, 1,134 to 192,447 U/L) were analyzed on both VetScan VS2 and Cobas c501 machines. Serum potassium concentrations were compared between the VetScan VS2 and ion-specific analyzers by Bland-Altman and Wilcoxon ranked tests and correlated to log10 CK activity via Pearson correlation. RESULTS: Serum potassium concentrations were significantly higher on the VetScan VS2 (6.7 ± 1.6 mmol/L) versus the ion-specific analyzers (4.0 ± 1.1 mmol/L; P < .0001), with high bias shown in Bland-Altman analysis (43.1 ± 27.9). Potassium concentrations positively correlated with log10 CK activity with the VetScan VS2 (R2 = 0.51; P = .003) but not the Cobas (R2 = 0.09; P = .3) analyzer. CLINICAL RELEVANCE: An alternate analyzer to the VetScan VS2 should be used to evaluate serum potassium concentrations in horses with rhabdomyolysis because the VetScan VS2 methodology uses lactate dehydrogenase, which increases in serum with rhabdomyolysis and falsely elevates potassium concentrations.

Comparing the health of refugee and asylee patients with that of non-refugee immigrant and US-born patients in a large Urban clinic.

OBJECTIVES: To compare disease burden in refugee/asylee, non-refugee immigrant, and US-born patients in the largest safety net clinic in San Francisco, California. METHODS: This is a retrospective chart review including 343 refugee/asylee, 450 immigrant, and 202 US-born patients in a San Francisco clinic from January 2014 to December 2017. Using electronic medical records, we compared prevalence of several diseases by immigration status. Using Poisson regression models with robust variance, we assessed association of diseases with immigration status, adjusting for sociodemographic characteristics. RESULTS: Diagnoses of non-communicable chronic diseases were less common in refugees/asylees, who had a greater risk of being diagnosed with mental health conditions. In Poisson regression models adjusted for sociodemographic characteristics, compared with refugees/asylees, US-born patients were more likely to have hypertension (IRR[CI] = 1.8 [1.0, 3.7]) and less likely to have depression (IRR[CI] = 0.5 [0.3, 0.8]). US-born (IRR[CI] = 0.06 [0.01, 0.2]) and immigrant patients (IRR[CI] = 0.1 [0.06, 0.2]) were less likely to have post-traumatic stress disorder. CONCLUSIONS: We uncover differences in burden of non-communicable chronic diseases and mental health by immigration status. These results highlight the importance of clinical screenings and research on disease burden in refugees.

Genome-wide CRISPR-Cas9 screen analyzed by SLIDER identifies network of repressor complexes that regulate TRIM24.

TRIM24 is an oncogenic chromatin reader that is frequently overexpressed in human tumors and associated with poor prognosis. However, TRIM24 is rarely mutated, duplicated, or rearranged in cancer. This raises questions about how TRIM24 is regulated and what changes in its regulation are responsible for its overexpression. Here, we perform a genome-wide CRISPR-Cas9 screen by fluorescence-activated cell sorting (FACS) that nominated 220 negative regulators and elucidated a regulatory network that includes the KAP1 corepressor, CNOT deadenylase, and GID/CTLH E3 ligase. Knocking out required components of these three complexes caused TRIM24 overexpression, confirming their negative regulation of TRIM24. Our findings identify regulators of TRIM24 that nominate previously unexplored contexts for this oncoprotein in biology and disease. These findings were enabled by SLIDER, a new scoring system designed and vetted in our study as a broadly applicable tool for analysis of CRISPR screens performed by FACS.

Changes in operative otolaryngology infections related to the COVID19 pandemic: A retrospective cohort study.

BACKGROUND: Pediatric emergency admissions fell significantly during the COVID-19 pandemic. This study investigated the changes in severe infectious complications managed by otolaryngology between the pre-pandemic period and the first year of the pandemic to determine if COVID-19 or related public health measures influenced the rate or severity of presentations managed in otolaryngology. METHODS: A retrospective chart review was conducted on pediatric patients who presented with severe infectious otolaryngology presentations (acute mastoiditis, deep neck space abscesses, and orbital complications of sinusitis) over the pre-pandemic (March 2018-February 2020) and early pandemic (March 2020-February 2021) periods. Patient characteristics, details of presentation, treatment, and outcomes were extracted from patients' charts. Independent samples t-tests/Mann-Whitney U-tests for continuous variables and Pearson chi-squared tests/Fisher's exact test for categorical variables were conducted to compare the pre vs early pandemic groups. RESULTS: There were 93 pre-pandemic and 28 early pandemic presentations. The monthly case average was significantly lower during the early pandemic period than the 2 years prior [3.58 (2.80) vs 2.00 (2.00), P = .045]. The average monthly frequency of presentations for deep neck space abscess and mastoiditis were significantly higher in the pre-pandemic group when compared to the early pandemic group [1.96 (±0.33) vs 1.33 (±0.48), P = .049; .71 (±0.26) vs 0.17 (±0.41), P = .01, respectively]. The early pandemic group was significantly younger (3.81 vs 6.04 years, P = .005), however there were no differences in gender, length of admission, and days from symptom onset to presentation between the two groups (P > .05). The early pandemic group had significantly elevated inflammatory markers on presentation [CRP, WBC, neutrophils (P = .02, P = .02, P = .04, respectively)] compared to the pre-pandemic group. CONCLUSION: The COVID-19 pandemic has had an effect on severe infectious complications of ENT pathologies, including decreased average monthly cases during the early pandemic, younger age at presentation, and elevated inflammatory markers.

Current Topics in Medical Colic.

The list of medical causes of acute or chronic colic in horses is extensive. The purpose of this article is to review 4 medical causes of equine colic with a focus on newer trends in treatment. The 4 topics selected include gastric impaction, gastric glandular disease, colon displacement, and inflammatory bowel disease.

SARS-CoV-2 infection in technology-dependent children: a multicenter case series.

PURPOSE: The objective of this study was to describe the clinical course and outcomes in children with technology dependence (TD) hospitalized with SARS-CoV-2 infection. METHODS: Seventeen pediatric hospitals (15 Canadian and one each in Iran and Costa Rica) included children up to 17 years of age admitted February 1, 2020, through May 31, 2021, with detection of SARS-CoV-2. For those with TD, data were collected on demographics, clinical course and outcome. RESULTS: Of 691 children entered in the database, 42 (6%) had TD of which 22 had feeding tube dependence only, 9 were on supplemental oxygen only, 3 had feeding tube dependence and were on supplemental oxygen, 2 had a tracheostomy but were not ventilated, 4 were on non-invasive ventilation, and 2 were on mechanical ventilation prior to admission. Three of 42 had incidental SARS-CoV-2 infection. Two with end-stage underlying conditions were transitioned to comfort care and died. Sixteen (43%) of the remaining 37 cases required increased respiratory support from baseline due to COVID-19 while 21 (57%) did not. All survivors were discharged home. CONCLUSION: Children with TD appear to have an increased risk of COVID-19 hospitalization. However, in the absence of end-stage chronic conditions, all survived to discharge.

A Pediatric Investigators Collaborative Network on Infections in Children (PICNIC) multi-centre Canadian descriptive analysis of Haemophilus influenzae bacteremia in children: Emerging serotypes.

Background: There has been dramatic reduction in Haemophilus influenzae serotype b (Hib) since introduction of Hib vaccines, but children still experience serious invasive Haemophilus influenzae (Hi) disease caused by various serotype and non-typeable bacteria. The object of this study was to describe the serotype distribution and clinical spectrum of Hi bacteremia in children admitted to Canadian hospitals. Methods: All children with Hi bacteremia admitted 2013 through 2017 to 10 centres across Canada were included. Demographic, clinical, treatment and outcome data were collected. Results: Haemophilus influenzae bacteremia occurred in 118 children of median age 12 months (inter-quartile range: 7-48 months). Forty-three (36%) isolates were non-typeable (NTHi) and 8 were not typed. Of the 67 typeable (THi), Hia (H. influenzae serotype a) (n=36, 54%), Hif (serotype f) (n=19, 26%) and Hib (serotype b) (n=9, 13%) dominated. The THi was more likely than NTHi bacteremia to present as meningitis (p<0.001), particularly serotype a (p=0.04) and less likely to present as pneumonia (p<0.001). Complicated disease (defined as intensive care unit admission, need for surgery, long-term sequelae or death) occurred in 31 (26%) cases and were more likely to have meningitis (p<0.001) than were those with uncomplicated disease. Conclusion: In the era of efficacious conjugate Hib vaccines, NTHi, Hia and Hif have emerged as the leading causes of invasive Hi in Canadian children, with Hia being most likely to result in meningitis and complicated disease. A vaccine for all NTHi and THi would be ideal, but knowledge of the current disease burden from circulating strains will inform prioritization of vaccine targets.

Risk factors for severe PCR-positive SARS-CoV-2 infection in hospitalised children.

OBJECTIVE: To identify risk factors for severe disease in children hospitalised for SARS-CoV-2 infection. DESIGN: Multicentre retrospective cohort study. SETTING: 18 hospitals in Canada, Iran and Costa Rica from 1 February 2020 to 31 May 2021. PATIENTS: Children<18 years of age hospitalised for symptomatic PCR-positive SARS-CoV-2 infection, including PCR-positive multisystem inflammatory syndrome in children (MIS-C). MAIN OUTCOME MEASURE: Severity on the WHO COVID-19 Clinical Progression Scale was used for ordinal logistic regression analyses. RESULTS: We identified 403 hospitalisations. Median age was 3.78 years (IQR 0.53-10.77). At least one comorbidity was present in 46.4% (187/403) and multiple comorbidities in 18.6% (75/403). Eighty-one children (20.1%) met WHO criteria for PCR-positive MIS-C. Progression to WHO clinical scale score ≥6 occurred in 25.3% (102/403). In multivariable ordinal logistic regression analyses adjusted for age, chest imaging findings, laboratory-confirmed bacterial and/or viral coinfection, and MIS-C diagnosis, presence of a single (adjusted OR (aOR) 1.90, 95% CI 1.13 to 3.20) or multiple chronic comorbidities (aOR 2.12, 95% CI 1.19 to 3.79), obesity (aOR 3.42, 95% CI 1.76 to 6.66) and chromosomal disorders (aOR 4.47, 95% CI 1.25 to 16.01) were independent risk factors for severity. Age was not an independent risk factor, but different age-specific comorbidities were associated with more severe disease in age-stratified adjusted analyses: cardiac (aOR 2.90, 95% CI 1.11 to 7.56) and non-asthma pulmonary disorders (aOR 3.07, 95% CI 1.26 to 7.49) in children<12 years old and obesity (aOR 3.69, 1.45-9.40) in adolescents≥12 years old. Among infants<1 year old, neurological (aOR 10.72, 95% CI 1.01 to 113.35) and cardiac disorders (aOR 10.13, 95% CI 1.69 to 60.54) were independent predictors of severe disease. CONCLUSION: We identified risk factors for disease severity among children hospitalised for PCR-positive SARS-CoV-2 infection. Comorbidities predisposing children to more severe disease may vary by age. These findings can potentially guide vaccination programmes and treatment approaches in children.

p53 Activation Paradoxically Causes Liver Cancer.

Activation of p53 regulates a transcriptional program that can cause cell cycle arrest, senescence, apoptosis, and ferroptosis, which are potent tumor suppressive mechanisms. Unexpectedly, Makino and colleagues show in this issue of Cancer Research that the constitutive activation of p53 in murine hepatocytes leads to tumor development. Detailed analyses indicate that p53 activation leads to loss of hepatocytes, increased expression of chemokines and humoral factors, and expansion of the hepatic progenitor cell population. These progenitor cells are highly proliferative, show chromosomal instability, and eventually transform. In chronic liver disease in humans, activation of p53 is associated with increased liver cancer development. This study highlights the complexity and non-cell autonomous nature of the physiologic p53 response. See related article by Makino et al., p. 2860.

Duration of Antibiotic Therapy and Timing of Shunt Reimplantation in Pediatric CSF Shunt Infections: A Retrospective Multicenter Case Series.

In this retrospective multicenter series of 154 children with cerebrospinal fluid shunt infections, the median (interquartile range) duration of antibiotic therapy was 18 (14-26) days. The time to shunt replacement was 14 (10-19) days. Management appeared to potentially differ according to the targeted pathogen and site.

Predictors of severe illness in children with multisystem inflammatory syndrome after SARS-CoV-2 infection: a multicentre cohort study.

BACKGROUND: SARS-CoV-2 infection can lead to multisystem inflammatory syndrome in children (MIS-C). We sought to investigate risk factors for admission to the intensive care unit (ICU) and explored changes in disease severity over time. METHODS: We obtained data from chart reviews of children younger than 18 years with confirmed or probable MIS-C who were admitted to 15 hospitals in Canada, Iran and Costa Rica between Mar. 1, 2020, and Mar. 7, 2021. Using multivariable analyses, we evaluated whether admission date and other characteristics were associated with ICU admission or cardiac involvement. RESULTS: Of 232 children with MIS-C (median age 5.8 yr), 130 (56.0%) were male and 50 (21.6%) had comorbidities. Seventy-three (31.5%) patients were admitted to the ICU but none died. We observed an increased risk of ICU admission among children aged 13-17 years (adjusted risk difference 27.7%, 95% confidence interval [CI] 8.3% to 47.2%), those aged 6-12 years (adjusted risk difference 25.2%, 95% CI 13.6% to 36.9%) or those with initial ferritin levels greater than 500 µg/L (adjusted risk difference 18.4%, 95% CI 5.6% to 31.3%). Children admitted to hospital after Oct. 31, 2020, had numerically higher rates of ICU admission (adjusted risk difference 12.3%, 95% CI -0.3% to 25.0%) and significantly higher rates of cardiac involvement (adjusted risk difference 30.9%, 95% CI 17.3% to 44.4%). At Canadian sites, the risk of ICU admission was significantly higher for children admitted to hospital between December 2020 and March 2021 than those admitted between March and May 2020 (adjusted risk difference 25.3%, 95% CI 6.5% to 44.0%). INTERPRETATION: We observed that age and higher ferritin levels were associated with more severe MIS-C. We observed greater severity of MIS-C later in the study period. Whether emerging SARS-CoV-2 variants pose different risks of severe MIS-C needs to be determined.