BACKGROUND:While long coronavirus disease 2019 (COVID-19) is linked to prolonged vascular dysfunction in adults, research in children remains poor. In this study, we assessed vascular health in children infected with severe acute respiratory syndrome coronavirus 2 about 6.8 months postinfection, comparing them with healthy controls. METHODS:Two hundred twenty-three children were assessed and divided into group 1, which included children with a positive disease history and group 2, which consisted of healthy controls. Anthropometric measurements, lipid profile, biomarkers (interleukin-6, C-reactive protein, tumor necrosis factor-alpha and soluble intracellular adhesion molecule) and long COVID symptoms were assessed, along with pulse wave velocity (PWV) measurements and carotid intima-media thickness (cIMT) to evaluate aortic stiffness. RESULTS:Children in group 1 were older (mean age: 10.8 ± 3.2 years vs. 8.5 ± 2.8 years, P < 0.001) and had higher body mass index (20.3 ± 5.6 kg/m 2 vs. 18.4 ± 3.5 kg/m 2 , P < 0.001). PWV was increased in group 1 (5.02 ± 0.7 m/s vs. 4.7 ± 0.6, P < 0.001). However, vascular differences between the groups disappeared after adjusting for age, body mass index, and blood pressure. Soluble intracellular adhesion molecule-1 levels were elevated in children with a history of moderate/severe COVID-19 infection compared with controls (555.8 ± 113.2 ng/mL vs. 428 ± 42.6 ng/mL, P < 0.001). Cholesterol levels, inflammatory markers and cIMT were comparable between groups. Long COVID symptoms were reported mainly by participants of group 1 [34 (23.6%) vs. 3 (3.8%), P < 0.001]. CONCLUSIONS:This study demonstrates insights into the long-term effects of COVID-19 infection in children. Evidence of endothelial activation without structural arterial changes was found. Persistent inflammation postinfection was absent, yet approximately one-quarter of the participants experienced long COVID symptoms, indicating potential differences in the pathophysiology of postacute COVID-19 infection in childhood.

Background: Antibody levels decline a few months post-acute COVID-19, but humoral memory persists in adults. Age and disease severity may affect antibody responses. This study aims to evaluate the presence and durability of antibody responses in children with COVID-19. Methods: A prospective, single-center study, involving unvaccinated children 0–16 years of age who were hospitalized with COVID-19 between October 2020 and December 2021, was conducted. Serological testing for anti-Spike severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG and neutralizing antibodies was performed at diagnosis and at 1-, 3-, 6- and 12-months post-infection. Results: A total of 65 immunocompetent children were enrolled [mean age (±SD): 6.7 (±6.4) years; males: 56.9%]. At 3 months, 40/44 (91%) children were seropositive; seropositivity persisted in 22/26 (85%) children at 6 months and in 10/12 (83%) children at 12 months. There was no evidence that age was modifying the prediction of variance of SARS-CoV-2 IgG levels. In contrast, SARS-CoV-2 IgG levels varied with time and disease severity. The association with time was non-linear, so that with increasing time there was a significant reduction in SARS-CoV-2 IgG levels [coef, 0.044 (95% confidence interval {CI}: 0.061–0.028), P < 0.001]. For each increment of time, the higher disease severity group was associated with 0.9 lower SARS-CoV-2 IgG levels. Everyone varied from the average effect of time with an SD of 0.01, suggesting that individuals may have different trajectories across time. Conclusion: Disease severity, but not age, influences antibody titers among children hospitalized with COVID-19. SARS-CoV-2 infection induces durable seroconversion in these children with detectable IgG levels at 1 year after infection.

Multisystem inflammatory syndrome in children (MIS-C) is a rare but severe hyperinflammatory condition that may occur following SARS-CoV-2 infection. This retrospective, descriptive study of children hospitalized with multisystem inflammatory syndrome in children (MIS-C) in 12 tertiary care centers from 3/11/2020 to 12/31/2021. Demographics, clinical and laboratory characteristics, treatment and outcomes are described. Among 145 patients (95 males, median age 8.2 years) included, 123 met the WHO criteria for MIS-C, while 112 (77%) had serological evidence of SARS-CoV-2 infection. Fever was present in 99%, gastrointestinal symptoms in 77%, mucocutaneous involvement in 68% and respiratory symptoms in 28%. Fifty-five patients (38%) developed myocarditis, 29 (20%) pericarditis and 19 (13%) coronary aneurysms. Among the above cases 11/55 (20%), 1/29 (3.4%) and 5/19 (26.3%), respectively, cardiac complications had not fully resolved at discharge. Underlying comorbidities were reported in 18%. Median CRP value was 155 mg/l, ferritin 535 ng/ml, PCT 1.6 ng/ml and WBC 14.2 × 10 9 /mm 3 . Most patients had elevated troponin (41.3%) and/or NT-pro-BNP (49.6%). Intravenous immunoglobulin plus corticosteroids were used in 117/145 (80.6%), monotherapy with IVIG alone in 13/145 (8.9%) and with corticosteroids alone in 2/145 (1.3%). Anti-IL1 treatment was added in 15 patients (10.3%). Thirty-three patients (23%) were admitted to the PICU, 14% developed shock and 1 required ECMO. Mortality rate was 0.68%. The incidence of MIS-C was estimated at 0.69/1000 SARS-CoV-2 infections. Patients who presented with shock had higher levels of NT-pro-BNP compared to those who did not ( p < 0.001). Acute kidney injury and/or myocarditis were associated with higher risk of developing shock. Conclusion : MIS-C is a novel, infrequent but serious disease entity. Cardiac manifestations included myocarditis and pericarditis, which resolved in most patients before discharge. Timely initiation of immunomodulatory therapy was shown to be effective. NT-pro-BNP levels may provide a better prediction and monitoring of the disease course. Further research is required to elucidate the pathogenesis, risk factors and optimal management, and long-term outcomes of this clinical entity. What is Known: • MIS-C is an infrequent but serious disease entity. • Patients with MIS-C present with multi-organ dysfunction, primarily involving the gastrointestinal and cardiovascular systems. What is New: • NT-pro-BNP levels may provide a better prediction and monitoring of the disease course. • Acute kidney injury and/or myocarditis were associated with higher risk of developing shock.