Monte Carlo Regression for Evaluating Children's Role in the Pandemic Spread on the Example of Delta COVID-19 Wave.

BACKGROUND: The children's role in transmitting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the familial settings is uncertain. We aimed to assess how often children were the index cases transmitting SARS-CoV-2 into their households during the Delta wave, and to identify risk factors of children being the index case. METHODS: In this prospective survey study, we collected information regarding household members of SARS-CoV-2-positive children tested in a single tertiary hospital. Some patients were tested with polymerase chain reaction and those samples were typed and classified as Delta or non-Delta variant. We have used the Monte Carlo approach to assess predictors of children being the index case in the household. RESULTS: We surveyed 629 families and 515 of them fulfilled inclusion criteria. The child was the index case in 359 (69.71%) households. Attending childcare facilities in all age groups was positively associated with being the index case in the household [nursery, estimate = 1.456, 95% confidence interval (CI): 1.456-1.457, P < 0.001; kindergarten, estimate = 0.899, 95% CI: 0.898-0.900, P = 0.003; school, estimate = 1.23, 95% CI: 1.229-1.231, P = 0.001]. The same association was present in the subgroup of the families with the predominant Delta variant, but not in the subgroup with the predominant non-Delta variant. CONCLUSIONS: Attending childcare and educational facilities might be a significant predictor of a child being the SARS-CoV-2 index case in their household. Children's role in driving the SARS-CoV-2 pandemic changes in consecutive waves. The Monte Carlo approach can be applied to assess risk factors of infectious agents' spread in future epidemics.

Recurrent assessment of lymphocyte subsets in 32 patients with multisystem inflammatory syndrome in children (MIS-C).

BACKGROUND: Lymphopenia is a hallmark of multisystem inflammatory syndrome in children (MIS-C). We aimed to characterize lymphocyte subsets' shifts and their correlations with other severity markers of MIS-C. METHODS: In this prospective cross-sectional study, we performed peripheral lymphocyte phenotyping in 32 patients with MIS-C. We analyzed lymphocyte subsets at three time points of the disease: the acute (A), convalescent (B), and recovery (C) phases. Based on age-normalized lymphocyte counts, we distinguished two groups of patients: "the mild" (higher lymphocyte counts) and "the severe" (lower lymphocyte counts). In addition, we examined differences between these groups regarding other severity markers. RESULTS: In phase A, 84% of children had lymphopenia. Decreased absolute counts of CD3, CD4, and CD8 cells were observed in, respectively, 88%, 72%, and 84% of patients. The natural killer cells were decreased in 63% and CD19 in 59% of children. "The severe" group had significantly higher procalcitonin and troponin I levels and lower platelets and albumin. Moreover, "the severe" group had hypotension more frequently (73% vs. 20%, p = .008). In phase B, all lymphocyte counts increased, and 32% of children had lymphocytosis. The increase of CD3, CD4, and CD8 counts correlated with some laboratory severity markers (hemoglobin, procalcitonin, D-dimer, lactate dehydrogenase, N-terminal prohormone of brain natriuretic peptide, albumin), but not with steroid use. In phase C, most children had normal lymphocyte counts. CONCLUSIONS: Substantial shifts in lymphocyte counts during MIS-C apply most to T lymphocytes and correlate with the disease severity markers, particularly hypotension prevalence. A proportion of children with MIS-C develops transient lymphocytosis during convalescence.