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ImportanceMultisystem inflammatory syndrome in children (MIS-C) is the most severe life-threatening clinical entity associated with pediatric SARS-CoV-2 infection. Whether COVID-19 mRNA vaccine can induce this complication in children is unknown. ObjectiveTo assess the risk of hyper-inflammatory syndrome following COVID-19 mRNA vaccine in children. Design, Setting, and ParticipantsPost-authorization national population-based surveillance using the French enhanced pharmacovigilance surveillance system for COVID-19 vaccines. All cases of suspected hyper-inflammatory syndrome following COVID-19 mRNA vaccine in 12- 17-year-old children between June 15th, 2021 and January 1st, 2022, were reported. Each case was assessed for WHO MIS-C criteria. Causality assessment followed 2019 WHO recommendations. ExposureCOVID-19 mRNA vaccine. Main Outcome and MeasuresThe main outcome was the reporting rate of post-vaccine hyper-inflammatory syndrome per 1,000,000 COVID-19 mRNA vaccine doses in 12-17-year-old children. This reporting rate was compared to the MIS-C rate per 1,000,000 12-17-year-old children infected by SARS-CoV-2. Secondary outcomes included the comparison of clinical features between post-vaccine hyper-inflammatory syndrome and post SARS-CoV-2 MIS-C. ResultsFrom June 2021 to January 2022, 8,113,058 COVID-19 mRNA vaccine doses were administered to 4,079,234 12-17-year-old children. Among them, 9 presented a multisystemic hyper-inflammatory syndrome. All cases fulfilled MIS-C WHO criteria. Main clinical features included male predominance (8/9, 89%), cardiac involvement (8/9, 89%), digestive symptoms (7/9, 78%), coagulopathy (5/9, 54%), cytolytic hepatitis (4/9, 46%), and shock (3/9, 33%). 3/9 (33%) required intensive care unit transfer, and 2/9 (22%) hemodynamic support. All cases recovered. Only three cases had evidence of previous SARS-CoV-2 infection. The reporting rate was 1.1 (95%CI [0.5; 2.1]) per 1,000,000 doses injected. As a comparison, 113 MIS-C (95%CI [95; 135]) occurred per 1,000,000 12-17-year-old children infected by SARS-CoV-2. Clinical features (inflammatory parameters, cytopenia) slightly differed from post-SARS-CoV-2 MIS-C, along with short-term outcomes (less PICU transfer than MIS-C). Conclusion and RelevanceVery few cases of hyper-inflammatory syndromes with multi-organ involvement occurred following COVID-19 mRNA vaccine in 12-17-year-old children. The low reporting rate of this syndrome, compared to the rate of MIS-C among same age children infected by SARS-CoV-2, supports the benefit of SARS-CoV-2 vaccination in children. Further studies are required to explore specific pathways of this entity compared to post-SARS-CoV-2 MIS-C. Key pointsO_ST_ABSQuestionC_ST_ABSIs COVID-19 mRNA vaccine in 12-17-year-old children associated with subsequent multisystemic hyper-inflammatory syndrome? FindingsThe French national pharmacovigilance system identified 9 children with a hyper-inflammatory syndrome with multi-organ involvement following COVID-19 mRNA vaccination (reporting rate 1.1 [0.5; 2.1] per 1,000,000 doses), of which only three had evidence of previous SARS-CoV-2 infection. All cases fulfilled WHO definition for MIS-C, but clinical and immunological features, along with short-term outcomes, slightly differed from classical post SARS-CoV-2 MIS-C. MeaningVery rare cases of hyper-inflammatory syndrome can occur following COVID-19 mRNA vaccine in 12-17-year-old children. The very low rate of this entity, compared to classical post-SARS-CoV-2 MIS-C, supports the benefit of SARS-CoV-2 vaccination in children.
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Among immune cells, activated monocytes play a detrimental role in chronic and viral-induced inflammatory pathologies. The uncontrolled activation of monocytes and the subsequent excessive production of inflammatory factors damage bone-cartilage joints in Juvenile Idiopathic Arthritis (JIA), a childhood rheumatoid arthritis (RA) disease. Inflammatory monocytes also exert a critical role in the cytokine storm induced by SARS-CoV2 infection in severe COVID-19 patients. The moderate beneficial effect of current therapies and clinical trials highlights the need of alternative strategies targeting monocytes to treat RA and COVID-19 pathologies. Here, we show that targeting CXCR4 with small amino compound such as the histamine analogue clobenpropit (CB) inhibits spontaneous and induced-production of a set of key inflammatory cytokines by monocytes isolated from blood and synovial fluids of JIA patients. Moreover, daily intraperitoneal CB treatment of arthritic mice results in significant decrease in circulating inflammatory cytokine levels, immune cell infiltrates, joints erosion, and bone resorption leading to reduction of disease progression. Finally, we provide the prime evidence that the exposure of whole blood from hospitalized COVID-19 patients to CB significantly reduces levels of key cytokine-storm-associated factors including TNF-, IL-6 and IL-1{beta}. These overall data show that targeting CXCR4 with CB-like molecules may represent a promising therapeutic option for chronic and viral-induced inflammatory diseases.
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SARS-CoV-2 infection in children is generally milder than in adults, yet a proportion of cases result in hyperinflammatory conditions often including myocarditis. To better understand these cases, we applied a multi-parametric approach to the study of blood cells of 56 children hospitalized with suspicion of SARS-CoV-2 infection. The most severe forms of MIS-C (multisystem inflammatory syndrome in children related to SARS-CoV-2), that resulted in myocarditis, were characterized by elevated levels of pro-angiogenesis cytokines and several chemokines. Single-cell transcriptomic analyses identified a unique monocyte/dendritic cell gene signature that correlated with the occurrence of severe myocarditis, characterized by sustained NF-{kappa}B activity, TNF- signaling, associated with decreased gene expression of NF-{kappa}B inhibitors. We also found a weak response to type-I and type-II interferons, hyperinflammation and response to oxidative stress related to increased HIF-1 and VEGF signaling. These results provide potential for a better understanding of disease pathophysiology.
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BackgroundChildren have a lower rate of COVID-19, potentially related to cross-protective immunity conferred by seasonal coronaviruses (HCoVs). We tested if prior infections with seasonal coronaviruses impacted SARS-CoV-2 infections and related Multisystem Inflammatory Syndrome (MIS). MethodsThis cross-sectional observational study in Paris hospitals enrolled 739 pauci or asymptomatic children (HOS group) plus 36 children with suspected MIS (MIS group). Prevalence, antigen specificity and neutralizing capability of SARS-CoV-2 antibodies were tested. Antibody frequency and titres against Nucleocapsid (N) and Spike (S) of the four seasonal coronaviruses (NL63, HKU1, 229E, OC43) were measured in a subset of seropositive patients (54 SARS-CoV-2 (HOS-P subgroup) and 15 MIS (MIS-P subgroup)), and in 118 matched SARS-CoV-2 seronegative patients (CTL subgroup). FindingsSARS-CoV-2 mean prevalence rate in HOSP children was 11.7% from April 1 to June 1. Neutralizing antibodies were found in 55{middle dot}6% of seropositive children, and their relative frequency increased with time (up to 100 % by mid-May). A majority of MIS children (25/36) were SARS-CoV-2 seropositive, of which all tested (n=15) had neutralizing antibodies. On average, seropositive MIS children had higher N and S1 SARS-CoV-2 titres as compared to HOS children. Patients from HOS-P, MIS-P, and CTL subgroups had a similar prevalence of antibodies against the four seasonal HCoVs (66{middle dot}9 -100%). The level of anti-SARS-CoV-2 antibodies was not significantly different in children who had prior seasonal coronavirus infection. InterpretationPrior infection with HCoVs does not prevent SARS-CoV-2 infection and related MIS in children. Children develop neutralizing antibodies after SARS-CoV-2 infection. Evidence before this studyChildren seem to be less likely affected by SARS-CoV-2 infection and clinical course of COVID-19 is less severe than in adults. As those asymptomatic or mildly symptomatic children are underdiagnosed and their viral loads are comparable to those of adults, they may act as an asymptomatic reservoir for the spread of the virus. One explanation of the difference between the adult and the pediatric infectious profile might be that infection with seasonal human coronaviruses, which is very frequent from a very young age, could lead to cross protective immunity. We searched in PubMed, MedRxiv and BioRxiv for publications from inception to June 15, 2020, using the terms "COVID-19, SARS-CoV-2, children, serology, Kawasaki, Corona Virus". Added value of this studySARS-CoV-2 mean prevalence rate was 11.7% from April 1 to June 1 and neutralizing antibodies were found in 55% of the tested seropositive children. Among patients with a Multisystem Inflammatory Syndrome, Kawasaki-like disease, 70% were SARS-CoV-2 seropositive and had neutralizing antibodies. COVID-19 and MIS attack rates, and anti-SARS-CoV-2 antibodies titres were not significantly impacted by prior seasonal coronavirus infection. Implications of all the available evidencePrior infection by seasonal coronaviruses does not prevent SARS-CoV-2 infection and associated Multisystem Inflammatory Syndrome in children As antibodies against seasonal coronaviruses are very frequent and as these viruses circulate efficiently in human populations every winter, our results question to what extent the concept of herd immunity based on circulating antibodies can be applied to seasonal coronaviruses and possibly SARS-CoV-2.
