Background: The aim of this study was to analyze the lung ultrasound (LUS) patterns in combination with clinical-laboratory profiles of children hospitalized for COVID-19 infection in relation to temporal trend of the Italian epidemic. Methods: This was a retrospective study conducted at a pediatric tertiary referral hospital from 15th March 2020 to 15th March 2021. We compared the characteristics of two periods of the pandemic outbreak, the first one in spring and summer (15th March-30th September 2020) and the second one in autumn and winter (1st October 2020-15th March 2021). Results: 28 patients (53.85%) were in the first period, 24 patients (46.15%) were in the second period. The disease severity score was significantly higher in the second period (p=0.02). We observed that the occurrence of the irregular pleural line was seen more frequently in the second period (87.5% vs 60.71%; p=0.03). The B-lines were significantly more frequent in children in the second period (87.5% vs 60%; p=0.03). The several but not-coalescent B-lines were significantly more frequent in the second period (80% vs 41.7%; p=0.05). The LUS score correlated significantly with the disease severity score with a strong relationship (r=0.51, p=0.002). The second phase of the COVID-19 epidemic outbreak had a higher disease severity score than the first phase with a moderate correlation (r= 0.42; p=0.01). Conclusion: The LUS plays an important role in the evaluation of pulmonary involvement in children affected by COVID-19 during different periods of the pandemic in combination with clinical-laboratory findings.

BACKGROUND: Despite SARS-CoV-2 immunizations have started in most countries, children are not currently included in the vaccination programs, thus it remains crucial to define their anti-SARS-CoV-2 immune response in order to minimize the risk for other epidemic waves. This study seeks to provide a description of the virology ad anti-SARS-CoV-2 immunity in children with distinct symptomatology. METHODS: Between March and July 2020, we recruited 15 SARS-CoV-2 asymptomatic (AS) and 51 symptomatic children (SY), stratified according to WHO clinical classification. We measured SARS-CoV-2 viral load using ddPCR and qPCR in longitudinally collected nasopharyngeal swabs samples. To define anti-SARS-CoV-2 antibodies we measured neutralization activity and total IgG load (Diasorin). We also evaluated antigen-specific B and CD8+T-cells, using a labelled S1+S2 protein and ICAM expression, respectively. Plasma protein profiling was performed with Olink. RESULTS: Virological profiling showed that AS had lower viral load at diagnosis (p=0.004) and faster virus clearance (p=0.0002) compared to SY. Anti-SARS CoV-2 humoral and cellular response did not appear to be associated with the presence of symptoms. AS and SY showed similar titers of SARS-CoV-2 IgG, levels of neutralizing activity, and frequency of Ag-specific B and CD8+T-cells. Whereas pro-inflammatory plasma protein profile was associated to symptomatology. CONCLUSION: We demonstrated the development of anti-SARS-CoV-2 humoral and cellular response with any regards to symptomatology, suggesting the ability of both SY and AS to contribute towards herd immunity. The virological profiling of AS suggested that they have lower virus load associated with faster virus clearance.