Background: Persistence of protective immunity for SARS-CoV-2 is important against reinfection. Knowledge on SARS-CoV-2 immunity in pediatric patients is currently lacking. We opted to assess the SARS-CoV-2 adaptive immunity in recovered children and adolescents, addressing the pediatrics specific immunity towards COVID-19. Method: Two independent assays were performed to investigate humoral and cellular immunological memory in pediatric convalescent COVID-19 patients. Specifically, RBD IgG, CD4+, and CD8+ T cell responses were identified and quantified in recovered children and adolescents. Results: SARS-CoV-2-specific RBD IgG detected in recovered patients had a half-life of 121.6 days and estimated duration of 7.9 months compared with baseline levels in controls. The specific T cell response was shown to be independent of recovery time. Both CD4+ and CD8+ T cells showed robust responses not only to spike (S) peptides (a main target of vaccine platforms) but were also similarly activated when stimulated by membrane (M) and nuclear (N) peptides. Importantly, we found the differences in the adaptive responses were correlated with the age of the recovered patients. The CD4+ T cell response to SARS-CoV-2 S peptide in children aged <12 years correlated with higher SARS-CoV-2 RBD IgG levels, whereas higher level of CD8+ T cells in children aged ≥12 years, suggesting the importance of a T cell-dependent humoral response in younger children under 12 years. Conclusion: Both cellular and humoral immunity against SARS-CoV-2 infections can be induced in pediatric patients. Our important findings provide fundamental knowledge on the immune memory responses to SARS-CoV-2 in recovered pediatric patients.

Transplant-associated thrombotic microangiopathy (TA-TMA) is an under-recognized yet potentially devastating complication of hematopoietic stem cell transplantation which had increased awareness in recent years. This report summarizes territory-wide experience of paediatric TA-TMA in the Hong Kong Children’s Hospital from 1 April 2019 to 31 March 2021. Total six patients were identified among 73 transplants performed. Median duration of onset was 2.5 months post-HSCT. Three patients died while all 3 survivors suffered from stage 2 to 5 chronic kidney disease despite administration of eculizumab. To conclude, recognition and diagnosis of TA-TMA is challenging. Clinical utility of complement blockage with eculizumab is limited.

Purpose We evaluated the existing risk assessment tools for CML in children. Patients and Methods A total of 55 patients from 1.4 to 18.0 years with newly diagnosed CML between 1996 and 2019 were included. Forty-nine patients presented in the chronic phase, thirty-six of whom were treated with upfront tyrosine kinase inhibitor (CP-TKI group); one presented in the accelerated phase and 4 in the blastic phase. Treatment, survival, responses, and tolerance were evaluated. Results The median follow-up time was 8.7 years (range, 2 months to 24.3 years). All patients in the CP-TKI group received imatinib as their first TKI treatment. Allogenic stem cell transplantation was performed in one patient after complete cytogenetic response was achieved with imatinib and in one patient with imatinib failure. Dasatinib and nilotinib were prescribed as second-line TKI in 5 patients and 4 patients respectively. The 10-year overall survival (OS), progression-free survival (PFS) and event-free survival (EFS) of TKI treated group was 97%, 91.4% and 72.3% respectively. The rates of major molecular response and deep molecular response of TKIs were 81.2% and 67.5% at 60 months. The EUTOS long-term survival (ELTS) risk grouping did not predict OS, PFS or EFS. The IMAFAIL risk groups are correlated with the risk of imatinib failure. Conclusion TKIs resulted in excellent long-term overall and progression-free survival in children and adolescents with newly diagnosed CML in the chronic phase. Further studies are required to modify the existing prognostic scoring system or develop new ones for children.

Jejunal feeding is increasingly utilized in the pediatric population to reduce gastroesophageal reflux or aspiration pneumonia. We describe a pediatric patient who developed persistent neutropenia and anemia secondary to copper deficiency after more than one year of exclusive jejunal feeding. Bone marrow aspiration and trephine biopsy showed vacuolated myeloid and erythroid precursors compatible with copper deficiency. Short term treatment with mineral mixture powder including copper reversed the hematological abnormalities. This report highlights the risk of micronutrient deficiency and the haematological manifestations as a result of acquired copper deficiency in pediatric patients receiving long term jejunal feeding.